ListPlot: individual point colors - wolfram-mathematica

Question

I've got a simple ListPlot like
list2 = Table[{x, Sqrt[x]}, {x, 0, 100}];
Now I want to color specific points with RED, say every 5th point, I tried
mycolor[x_] /; Mod[x, 5] == 0 = Red;
mycolor[_] = Blue;
Now
ListPlot[#, PlotStyle -> AbsolutePointSize[3], ColorFunction ->
mycolor[#[[All, 1]], ColorFunctionScaling -> False]] &[list2]
doesnt work quite right, all points are still blue.
What is wrong here?
Thanks,
archi

Answer 1

Here is an easy way to get the result you're after :-
list2 = Table[{x, Sqrt[x]}, {x, 0, 100}];
mycolor[x_] := If[Mod[x, 5] == 0, Red, Blue];
mycolors = mycolor /# list2[[All, 1]];
ListPlot[List /# list2,
PlotStyle -> Map[{AbsolutePointSize[3], #} &, mycolors]]
Alternatively, with a colour function, thanks to rm -rf's answer on george's link :-
list2 = Table[{x, Sqrt[x]}, {x, 0, 100}];
mycolor = Function[{x, y}, If[Mod[x, 5] == 0, Red, Blue]];
ListLinePlot[list2,
PlotStyle -> AbsolutePointSize[3], ColorFunction -> mycolor,
ColorFunctionScaling -> False] /. Line -> Point
Further to comment
For different plot markers I have reverted to the easy method. In order to apply different styles and plot markers in ListPlot the differently styled points have to be in separate lists, hence List /# list2. (Only two lists would actually be necessary though.)
Clear[mycolor];
list2 = Table[{x, Sqrt[x]}, {x, 0, 100}];
mycolor[x_] := If[Mod[x, 5] == 0,
{Red, "\[FilledUpTriangle]", 14},
{Blue, "\[FilledSmallCircle]", 6}];
mycolorspec = mycolor /# First /# list2;
ListPlot[List /# list2,
PlotMarkers -> Apply[Style[#2, FontSize -> #3, #1] &,
mycolorspec, {1}]]