Just some brainstorming here because I don't know what kind of flower you stamped or how big or little of an area you're trying to color:
use a stencil brush
use a bit of makeup sponge
use a dry waterbrush
use a blender pen
Instead of ink:
use pastels/chalks in those colors or similar colors
stamp on that color cardstock and fussycut
Hope that helps spark some more ideas!