You're talking about dying them by immersion? Or by setting them in dye-water? Or using different chemicals to induce different colours in the bloom? Or how? Because it depends on what you're trying to do.
i want to grow blue roses and wish to change it from the roots buy adding colouring which coulour is the best to do it???
Actually, white roses would be the best as there's no background colour to conflict. Never heard of a dye that is taken up by the roots and transmitted to the flowers, though. Sorry, but I don't think the idea will work.
Start with a white rose. It's usually better to start off with a rose on a bush. "Underwater" the rose bush - allow the soil to dry up a bit. Choose a 1/2 open flower and cut it with a long stem. Recut under water and discard the first 1/2 inch of the stem. Make a small wedge shaped cut on the stem, about 1/2 inch from the bottom of the stem. Put a drop of food dye on the cut and seal (I use plumber's silicone tape). Place the stem in tepid water. The blue dye should travel up the stem and into the leaves and flowers after about 24-48 hours. (I would use gloves - blue hands are not particularly cosmetically pleasing to look at!) I haven't achieved any consistent result with this method, but it's the unpredictability of that makes it fun. Commercial cut flower growers cut the roses in bud, and then mature them with their stems immersed with a dye solution - they likely want to keep the chemical identity of their dye a competitive secret!
