Begin by mixing about ½ cup of water in each glass. Then add about 1 teaspoon of food coloring in each of the six rainbow colors to create a different color in each glass. To create orange, mix half yellow and half red. To create purple mix half red and half blue.
Give each stem of a baby's breath a fresh cut and place in the colored water.
If some stems don't absorb the color after a few hours or over night, recut the stem and place it in the colored water again. There's no specific time to leave the flowers. Some of the flowers changed color within a few hours, some need to stay in the colored water overnight.
Once the desired color intensity is reached, remove the stem from the colored water and place it in regular clear water, and arrange as desired, or dry them to use as dried flowers. The pigmentation of the flowers will vary depending on how much food coloring you use, and how long you let the flowers stay in the colored water. You can also adjust the color palette by using different shades of dye.