In a situation like this where there is great color contrast, I like to use a neutral polyester thread (current favorite is Superior's Bottom Line in Silver (#623):
https://www.superiorthreads.com/the-...23-silver-cone
It gives just the right amount of thread definition to both the light and dark areas. This is critical for me, as then the emphasis seems to be on the quilting lines rather than on my mistakes!
Variegated thread, to me, often adds too much of another color dimension to the quilting; I never know if the dark portion of the thread will show up on light fabric or become relatively invisible on dark portions, and vice versa. Variegated thread has its uses, especially for machine embroidery, but it is rarely my choice for a quilting thread.