Producing readable coloured terminal output - terminal

I want to produce coloured output from a terminal program. My problem is that some people use a 'light' terminal theme, while others use a 'dark' one.
Is there a standard way of ensuring that my output will be readable for all "reasonable" terminal configurations (for some definition of reasonable)?

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Actual colors in MacOS Terminal don't match their values in Preferences

I am trying to build a Terminal theme in MacOS. The colors that are actually being displayed are slightly different from the hex colors I am setting. For example:
I am setting the background color to #292D3E here. But when I sample the color from the actual background, it is #24293B.
Why is this happening? It seems to do it with most of the colors. I suspect it has to do with Terminal only being able to use a limited palette? But I'm wondering why it would still allow me to enter it, and why it would still show the pasted value and not change it to the allowed value after I saved it if that were the case.

Why is Emacs syntax highlighting in Gnome terminal affected by terminal colour theming?

I'm using Emacs 24.3 under Ubuntu 14.04.1. I'd like to use it both via the GTK interface and the Gnome terminal with emacs -nw. Unfortunately, the colours for any theme that I use appear slightly different in the terminal.
I've set things up so that under Gnome terminal, TERM=xterm-256color. However, I have also customised my terminal colors — "black" is actually #151515, "red" is #DA4939, etc. Emacs seems to get close to displaying the correct colours for each theme, but is never quite correct. The themes I'm using are the deftheme-style of theme.
I don't understand why customising terminal colours should affect this — with TERM=xterm-256color, Emacs should have access to a greater palette than just the usual 16 colours. In the output of list-colors-display, black is listed as #000000 but displayed as #151515; there is, however, a color-16 that is also listed as #000000 and displayed properly. So Emacs is indeed capable of displaying #000000.
On the left is Emacs GTK, which displays the theme colours correctly. On the right is emacs -nw run in Gnome terminal, where all the colours are slightly different from what the theme specifies. The theme I've used for this picture is just an example; this happens with any theme. My full config is on Github.
How can I get Emacs to display the correct theme colours in Gnome terminal without removing my customisation of the terminal palette?
A couple issues:
1) I believe that when you customize the "terminal colours", they overlap the first 16 color entries of the 256-colour palette. So if emacs is telling the terminal to use colors 0-15, they will come out as whatever you have set that colour to actually be in your terminal preferences. It doesn't appear to be affecting you specifically, but it is good to be aware of.
2) For the remaining 256 colors, I believe there are only 256 (maybe 241 if your terminal re-colored the first 16) colors that you may choose from.
Unless you choose your GTK theme colors to match exact colours that are available in the 256 palette, having them be identical is not going to be possible. It looks like your emacs did a pretty good job of selecting the closest available colors of the 256 on its own.
If you want to see what I'm talking about in action, try downloading and running a script such as this show-all-256-colors.py script and running it in your terminal. I would wager that as you change your terminal colours, you'll see the entries 000 through 015 change correspondingly, while the remaining colors are always the same.

Change Clang's colored output

Is it possible to change Clang's choice of colors for their colorized diagnostics?
I like my terminal to have a black background, but I just noticed that I was missing Clang's helpful diagnostic messages. I'm aware of the the -fno-color-diagnostics compiler option but I would prefer to have the colors, just different colors. Any solutions?
I'm using a bash shell in OSX. Thanks.
It looks like the colors are hard-coded near the beginning of this file (include file). You can edit the file and recompile the program, write and submit a feature that accepts color settings at the command line, in an environment variable or from a file, or non-portably try to substitute the colors on the fly.
Here is an example of the latter:
clang ... | sed 's/\o33\[30m/\o33[37m/g'
That changes black to white for XTerm escape sequences. Some other sequence would need to be used for other terminal types.

Is there a way to copy text from emacs with faces in Windows?

Every now and then I run into a situation when I need to email a piece of code from emacs. When I paste text into my email program (not emacs), all the color highlighting is lost. This is especially disappointing when pasting from org-mode, which relies heavily on colors for readability. It would be good to preserve font faces.
Is there a way to do this? I am looking for output similar to that of ps-print-buffer-with-faces.
Suppose your email program can handle html, try M-xhtmlfontify-buffer, which converts the contents of the current buffer (with faces) to css-styled html.

Why does the 256-color palette change in terminal VIM on OS X?

I have been playing with color schemes for terminal VIM and have found something annoyingly frustrating that I have been unable to solve thus far.
I expect the 16 system colors to change. They are obviously configurable. For that reason, I attempted to use the 256-color palette to construct a VIM color scheme that would be the same regardless of the terminal's 16 (configurable) system color palette.
I used only colors from the 256 color palette for everything, including background. However, I noticed that if I open terminals with different background and text colors specified for the terminals, the VIM color schemes appear quite different in the two terminals.
I do not see similar behavior on Ubuntu even when the terminals have different background, foreground, AND system color palettes.
I will happily accept an answer that explains why this happens.
I will be ecstatic if someone can tell me a way around this beyond setting up a specific terminal for each set of color settings I want to use.
By default, ANSI terminals are 16 color devices and the Vim color schemes that work in gvim will not work properly in a terminal.
Some terminals are capable of 88 or 256 colors. You can tell Vim about this by setting t_Co. Of course, 256 colors is still less than full RGB that you have in gvim.
There is a package for vim called CSApprox developed by Matt Wozniski. It lets you use the gvim color schemes with approximate colors.
This is what I use myself.
CSApprox includes a documentation file which explains everything better than I can here.
URL: http://www.vim.org/scripts/script.php?script_id=2390
Good luck.
P.S. about your question However, I noticed that if I open terminals with different background and text colors specified for the terminals, the VIM color schemes appear quite different in the two terminals.
That sounds like the OSX terminal does not separate the color definition from the 256 color xterm palette; i.e. that by manipulating its settings you're messing with the palette or something like that.
Terminals should probably be keeping the 16 color user-configurable stuff separate from the 256 color palette.
Terminal dynamically adjusts some color values to ensure a minimum amount of contrast with the background color. Perhaps that’s what you’re seeing.
Please attach a screenshot showing the two different color schemes. A good script for viewing the available colors is 256colors2.pl.
Please, post screenshots so that we see what you see. It's hard to talk about colors without seeing them or comparing their numerical values.
Well, I'm still on 10.6.8 so I've never enjoyed Terminal.app's ability to display 256 colors.
But, AFAIK, its default 16 colors are not taken from the X11 palette. They are probably hardcoded somewhere and their values are user-configurable anyway. Because of that, I have no idea why changing the default Red value to anything would change the looks of your Vim colorscheme.
However, Terminal.app (like most other terminal emulators) allows you to change the values of Background, Text, Bold, Selection and Cursor. Depending on how your colorschemes are written some of these settings may override parts of your colorscheme, Background, most notably.
I've had my Terminal.app background matching my Vim colorscheme's background for a long while with great results. Well, at least for a 16 color terminal emulator.
The 256 colour mode is still just an indexed palette, the same as the 8 and 16 colour modes. The application simply selects a colour by index from a palette, and it's up to the terminal to decide which colour that will actually be.
That two different terminals happen to pick the same colours for these indexes may just be the fact that within the 216-colour RGB cube there's 6 levels of each component, so the "obvious" natural way to assign those colours would be to pick each from the list (0, 0x33, 0x66, 0x99, 0xcc, 0xff). I'd imagine most terminals will do this, and therefore give the same colours at the same indices.
If two terminals differ it's simply an indication they're using some other method of selecting their actual colours.
If you are using iTerm2 then you may need to change what type of terminal it is reporting.
In your iTerm2 Preferences > Profile > Terminal > Report Terminal Type, set to xterm-256color
In Terminal.app aka Apple Terminal, the colours will change if the background colour is not explicitly set as well.
So with your colour scheme you must set up the default background colour using the Normal colour group, e.g.:
hi Normal ctermfg=188 ctermbg=234
and then you should not see any further changes to colours.
Note: I have only noticed the foreground being affected presumably so that you do not miss any important output ;)

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