Ask Mr. Smarty Plants

How do I change the bloom color of what? In Alice in Wonderland, the gardener cards changed the white roses to red with a paint brush. It wasn't very successful and they were marked out to have their heads off, but Alice woke up so we'll never know how that came out.

We have been asked before how to change flower color. The only flower we have personal experience with changes of color is the Hydrangea. From the United States National Arboretum website on Hydrangea Questions and Answers, we found this excerpt about why the same species would be blue in one part of the country and pink in another. There are only two hydrangeas native to North America, Hydrangea arborescens (Wild hydrangea) and Hydrangea quercifolia (Oakleaf hydrangea). Only H. arborescens is native to Oklahoma.

"Flower color in H. macrophylla is dependent on cultivar and aluminum availability. Aluminum is necessary to produce the blue pigment for which bigleaf hydrangea is noted. Most garden soils have adequate aluminum, but the aluminum will not be available to the plant if the soil pH is high. For most bigleaf hydrangea cultivars, blue flowers will be produced in acidic soil (pH 5.5 and lower), whereas neutral to alkaline soils (pH 6.5 and higher) will usually produce pink flowers. Between pH 5.5 and pH 6.5, the flowers will be purple  or a mixture of blue and pink flowers will be found on the same plant."

Our experience with this was that hydrangeas came up naturally with blue flowers in the acidic soil of East Texas. In North Central Texas, with its alkaline soil, they came up pink.

From All About Gardening, here is an article on factors that influence a flower's color.

From WillTaft.com, Do Iris Flowers Change Color? From that, notice this paragraph on artificially changing bloom colors:

 "Also, you can’t change the color of an iris by changing the soil pH., or anything else in the soil. That sometimes works with hydrangeas, but not with any other plants that I know of.  The color of an iris, for example,  is a result of its genetics.  The rhizome of an iris that produces a purple flower will continue to produce that same color."

So, we still are not sure what you were asking, but we've told you about all we know about the subject. Trying to alter the soil to induce plants to bloom in an unnatural color doesn't work. Even with aluminum additives in alkaline soil, the change to blue of hydrangea blooms will not last long as the additives are absorbed and move in the soils.

We don't recommend paint.