Not able to style Excel with spreadsheet gem (Ruby) - ruby

Question

Trying to style an excel following - ruby spreadsheet row background color but nothing is happening for me -
Here goes my code -
My formats:
pass_format = Spreadsheet::Format.new :color=> :blue, :pattern_fg_color => :green, :pattern => 1
fail_format = Spreadsheet::Format.new :color=> :blue, :pattern_fg_color => :red, :pattern => 1
skip_format = Spreadsheet::Format.new :color=> :blue, :pattern_fg_color => :yellow, :pattern => 1
Trying to use them here(just showing one rest are decided by if elses):
sheet1.row(counter).default_format = skip_format
sheet1[counter, 3] = 'Skipped'
sheet1.row(counter).default_format = skip_format
sheet1.row(counter).set_format(3, skip_format)
Counter is the row I am currently in. Here I am not sure whether I should format first or write first. What am I doing wrong? How to fix this?
Actually it's getting applied as I found from .inspect-
#<Spreadsheet::Format:0x007f082f9c1d58 #font=#<Spreadsheet::Font:0x007f082f9c1a88 #name="Arial", #color=:red, #previous_fast_key=nil, #size=nil, #weight=nil, #italic=nil, #strikeout=nil, #outline=nil, #shadow=nil, #escapement=nil, #underline=nil, #family=:swiss, #encoding=nil>, #number_format="GENERAL", #rotation=0, #pattern=1, #bottom_color=:black, #top_color=:black, #left_color=:black, #right_color=:black, #diagonal_color=:black, #pattern_fg_color=:yellow, #pattern_bg_color=:pattern_bg, #regexes={:date=>/[YMD]/, :date_or_time=>/[hmsYMD]/, :datetime=>/([YMD].*[HS])|([HS].*[YMD])/, :time=>/[hms]/, :number=>/[#]/}, #used_merge=0>
but even if it shows color red here in excel it's black. :(
I am editing the original file then writing in a new file as
book.write "Result.xls"
Is it the wrong approach? I am going to try to make a new workbook before editing and update.

Answer 1

Well, it was not possible to format the existing excel then write it as a new Excel. Formatting was lost in that.
To overcome I created a new excel (populated with my existing data read from the old excel) formatted it as I want then used
book.write "xxx.xls"