Color is not saved properly

The problem was incorrectly assuming that color components were 8-bit (as they appear in the color chooser dialog):

class Gdk::Color
  def to_hex
    sprintf('#%x%x%x', red, green, blue)
  end
end

Gdk::Color components are in fact 16-bit.

Revision 12 looks like this:

class Gdk::Color
  def to_hex
    sprintf('#%02x%02x%02x', red / 257, green / 257, blue / 257) # because 255 * 257 == 65535
  end
end

Using 257 does not look like it's correct. Are you really sure it is?

I agree it looks odd, but: http://www.google.com/search?q=gdk+color+257

just my 2 pence:
seems to be a common misapprehension: as 255 times 257 is 65535, some believe that by dividing 16 bit numbers by 257 they receive 8 bit numbers - but that's wrong. As integer division discards the remainder, what you get in fact is a mapping of 1 single 16 bit number (65535) to one 8 bit number and 255 mappings of 257 16 bit numbers each to one 8 bit number. This is wanted only in rare cases, where you want to make sure that only the maximum 16 bit number maps to the maximum a bit number. The common way to reduce 16 bit numbers to 8 bit is just to discard the lower 8 bits, and this is done by dividing by 256. This way 256 16 bit numbers always evenly map to one 8 bit number.