I'm afraid there isn't. With normal slot tinting (single color tinting) you can make it completely black or anywhere between black and full color. If you enable Tint black for the slot (two color tinting), you can make it completely white, completely black, or anywhere between those and full color or inverse full color.

One option could be to make your image grayscale, then use Tint black to get the coloring you want. If that is acceptable for the colored version, then you'd be able to use slot tinting to make it grayscale as you need. Nintendo uses this extensively. Check out the table with the Mario coin in the docs here:
Attachments - Spine User Guide: Tint black