Color nerd moment.
Some of the color discrepancies seem to stem from this Lucasfilm color guide to Fett's outfit:
I would assume that Sideshow used those Pantone color swatches to make this figure, but there are actually various categories of Pantone colors. The default is the Pantone Matching System (PMS), which is supposed to be their universal color space.
So the PMS colors, using those codes would be:
But notice that the colors have have the "U" suffix, meaning "Uncoated", which would actually give you this:
The uncoated versions are much more pale, but the PMS versions almost seem far too bright and intense. Honestly a lot of it has to do with the materials that the color is applied to. With the exception of the pale 491U Red, all the uncoated colors seem more film accurate.