Use custom colors with Spreadsheet gem

I need to use custom color and pattern_fg_color (HEX: 0x00adb1, RGB: 0,173,177). I was following advice from here, but it didn't work out for me (I am using it in another library based on the Spreadsheet gem):

Spreadsheet::Excel::Internals::SEDOC_ROLOC.update(enterprise: 0x00adb1)
Spreadsheet::Column.singleton_class::COLORS << :enterprise

Test example:

Spreadsheet::Format.new(pattern_fg_color: :enterprise)

And I get the following error:

unknown color 'enterprise'

Any suggestions would be appreciated greatly.

It seems that mapping an existing color to another hex/rgb code is much easier than adding a new one, so my solution implies that a built-in :xls_color_41 is changed.

Second approach

Actually, I've achieved the same result without monkey patching, using gem's native method Spreadsheet::Workbook#set_custom_color:

document = Spreadsheet::Workbook.new
document.set_custom_color(41, 0x00, 0xad, 0xb1) 

First approach:

I've ended up with monkey patching Spreadsheet::Excel::Writer::Workbook class: instead of default Excel '97 palette that was returned by default_palette method, I've defined a method, that changes returned palette for :xls_color_41 from [0x33, 0xcc, 0xcc] to [0x00, 0xad, 0xb1]. The result is as follows:

module Spreadsheet
  module Excel
    module Writer
      class Workbook  < Spreadsheet::Writer

        alias_method :excel_palette, :default_palette

        def palette_modifier
          {
            41 => [0x00, 0xad, 0xb1]
          }
        end

       def default_palette
         excel_palette.map.with_index{|rgb, code| [code, rgb]}.to_h.update( palette_modifier ).values
       end

      end
    end
  end
end