Here you can read a bit about the different types of paint and color that I like to use for crepe paper flowers.
Fruit color and coffee can be bought in regular supermarkets. Ink, watercolor paint, acrylic paint and PanPastel can be bought in many places online and in hobby/art shops.
Ink and fruit dye
I use inks e.g. of the brand Ecoline (not sponsored) or food coloring to color my crepe paper. Ink and food coloring work the same. You can get the ink in more shades of color - but fruit coloring is quite a bit cheaper. I use ink and food coloring to color my crepe paper wet. The disadvantage of this is that it takes several days before the paper is dry again and ready for use.
Plain instant coffee is what I most often use to color with. It can be used on its own, or mixed a little with water and fruit colouring/ink, so that you get a more muted and natural colour.
Pastel color - especially the brand PanPastel - works really well to add color to crepe paper flowers. The biggest advantage is that you can color with dry pastel and continue working on your flower right away because it doesn't get wet. You can also add a little extra color to a finished flower. PanPastel is a good choice if you don't want to wait days for your colored paper to dry.
I use watercolor paint in the form of a watercolor palette with a brush. My palette is from the Faber Castell (again not sponsored.. but I wish I where!) - but all watercolor palettes can be used. I use e.g. the watercolor paint to make small details on the petals of the paper flowers. You can also use a small pointed marker for the same purpose.
Acrylic paint adds a layer on the outside of the crepe paper. The downside to this is that it can give a slightly plastic-like appearance, especially if you use glossy acrylic paint. The advantage of acrylic paint is that it doesn't fade in sunlight. I only use acrylic paint for the green leaves and the stem of the flowers, because I find that the green crepe paper otherwise fades quickly.