synchronicity!

meaning...

I was just thinking about this!

I planted 2 crepe myrtles, 1 white & 1 pink, too close together a number of years ago, & this afternoon a neighbor asked me how I had managed to get pink flowers & white flowers on 1 crepe...

& I had to tell her, uh, actually, it's just 2 trees too close together.

but it made me think how pretty such a tree would be, with alternating white- & pink-blooming branches.

sort of like a carousel or a circus tent.

I hope there are some good suggestions!

I have never heard of anyone grafting crapes but in theory it should be possible. The simple side-wedge graft would be the style that I would suggest. If you have never grafted before than this is not the plant to learn on unless it is really more a curiousity idea. The next factor I would consider would be not only the color combinations but the vigor and size of the cultivars you would use as understock (usually referred to as a rootstock) and that you would graft onto this rootstock. The planting of known cultivars with similar growth (height and vigor) in the colors of your choosing likely would be the route I would suggest to be sure of your desired result.
Happy Growing David