The Year of the Three Roses was the fourth year of Discworld Stamps, and the Ankh-Morpork definitives were still on the same design with colours changed each year. The British Museum Discworld Stamp archive has sheets of the 2p Ankh, and 5p and 10p Morporkias for this particular year with a range of colours. There is a bit more to stamp production than merely choosing a new colour - one that hasn’t been used before. Colin Edwards, responsible for the overall final design, who want to ensure that not only that the colours used for this year’s stamps complemented each other, but also ‘sat’ well with those from previous years, in addition to being different to any others.

I suspect that Colin may have put these sheets together and submitted them to the shop as ideas or suggestions, in .pdf format. There they would have been printed out to get a good idea of how the stamps would look. Note that for each value there are three basic colours, and each of these comes in five slightly different degrees of lightness or intensity.