“Note that the conversions in this color codes chart are best described as ‘nominal’. They will produce an invertible conversion between the RGB code and a subset of CMYK; that is, one can take an RGB color code and convert to certain CMYK colors, and from these CMYK colors obtain the matching, original RGB codes. However, conversion of CMYK colors to RGB cannot be reversed; this means, given a CMYK color code which is converted to RGB, performing the former conversion may not give the original CMYK color.” (Thanks Coudal Partners!)