The blossoms were made with white, light-weight computer paper, on which I drew a star-shape (4 intersecting lines) with a purple non-waterproof marker pen. I wanted to see what would happen when the coloured 1/4" (6 mm) circles were dampened; my hope was that the colour would "run" in interesting ways. That part worked well, and I may try it with alcohol inks, as some people have suggested to me. Apparently, that is a technique taught in art schools.Also, the blossoms will not need to dry if using alcohol inks.
The colour variations add to the realism of the flowers. They are also flared differently, giving the appearance of flowers wide open and others still to open completely. The friend who wanted the plant components has decided it is too time-consuming and fiddly; unfortunately, that is the case with any and all petunia plants, they require lots of flowers. so this experiment is over.
Update (Posted August 30): I won't be trying the other idea I had, as the plants aren't needed now. Some day I may try to make some petunias for my own use, but Tudor medicinal gardens didn't have any use for petunias!