This is an issue with the original 1.1 mod as well, but when you're holding Fast belts in the cursor to try to place them, it's quite hard to determine which direction they're facing, and the same is true of the ghost belts.

For reddish hues in particular, the tinting used by the cursor selection / ghost shader makes the arrows very dark. On the vanilla sprites, the arrows are darker than the rest of the belt and it works out fine, but with this mod, it's almost indistinguishable.

Not sure what fix could be implemented to remedy this without changing the sprites themselves.
Maybe make it so that belts show a directional overlay when the cursor is on them, similar to inserters?
But I don't have a clue on how to code that. (Help would be appreciated.)

EDIT: I've tried defining a "radius visualization" but the result is pretty bad.