Ask Mr. Smarty Plants

Oh, gosh, sorry, our Magic Wand doesn't have a color-changing setting. There are a very few plants (hydrangeas being the only one that comes to mind) whose bloom color can be changed from pink to blue according to the soil they are growing in; pink for alkaline soil and blue for acidic soil. But we can find no indication that crape myrtle bloom colors can be altered. The crape myrtle is one of the most widely hybridized plants around, and each cross in the hybridization program requires a lot of time and care in getting just the right height, or bloom color or growing habit sought by the grower. To unravel how your particular trees acquired their lavender/pink color would require intricate retracing of the genetics involved, and you still couldn't change the colors of the ones you have. This University of Georgia Cooperative Extension Service website Crape Myrtle Culture lists a number of cultivars by color, etc. However, your best bet, if you want to purchase plants with a certain plant color, is to go to the nursery and actually see the colors of blooms before you buy the plant. And learn to love lavender/pink.