Small UI improvement for Sculpt mode: Change to Inverse Cursor color when holding CTRL (Inverse/Subtract mode))

You can specify a different color for Add/Subtract for brushes in sculpt mode, but it doesn't reflect it when you hold CTRL key for inverse/subtraction. It only works when you switch modes manually in the UI (+ and - buttons).

It would be a really nice visual queue, because I find myself having to CTRL+Z a lot of times, not knowing which mode I am in (+ or -)

Thank you very much for reading!

Cheers