There are times that using a crepe paper just as it is can be the best way to interpret a flower. Simple is best, for example, when making a gardenia - not much need for variation there. But, very often, switching up a color or creating an ombré or variegated paper will make your flower (or leaves) more interesting and realistic.
Matching colors to petals helps make the flower more realistic.
A note on different types of crepe
Single ply 60gm crepe: Iwill be honest and say that that I have never attempted anything but using a spray bottle of bleach or color on single ply. It’s a delicate paper and cannot take a lot of handling whether damp or wet. So, be cautious when attempting to vary the color this weight of crepe.
Doublette crepe can withstand a little more handling but will still tear very easily. The most durable of all the crepes is 180gm or 160gm crepe. The down side is it doesn’t take on color easily so you have to really work with it to get an over all color. The best techniques for this paper are either painting or splattering directly onto it or dipping its edges in a bleach solution or a dye to get an ombré effect.
Experimenting is absolutely the best way to find what works best for you.
Sunny days are when I color my papers and doing that outdoors is a guarantee of not making a total mess you’ll have to clean up later. And, don’t worry, the paper will dry long before the sun will have a chance to affect the color.