Thanks for reaching out. This doesn't look right. Please try re-installing XD and let us know if that solves the issue or if you need any further assistance.
Try to change windows icon size on desktop. You wil see that xd color icon change size and black icon become bigger. It as default. IMHO that is not a bug. It designed by defaul. Here is the optimal size that I catch. Then Pin it to taskbae
Thanks for the replies. I reinstalled XD and got my icon back. Definitely not an ideal solution.