To make these rainbow roses first you have to take water in three or more glasses. After that add food colors of different hues in each glass and mix well. At this step you can vary the amount of food color depending on how deep toned you want your roses to be. Then for example if you have three glasses split the bottom part of the stem of a white rose in three parts with a knife and immerse each part in one glass with food color. Be careful at this step not to break the upper part of the stem. Leave them until the rose absorbs the colored water and is dyed. Make more in the same way and complete a bunch.
A Bouquet of such rainbow roses can be great as a party centerpiece.