Not Prob: Onscreen display of Black & White

[photoken]

Win10 1607 x64
PL 20.50 x64

The colour White displays as a pale red, and the colour Black displays as a saturated red.

This is a screen capture of painting with a soft brush using White:

onscreen prob.jpg

This affects only the on-screen display. Exported images are correct.

Added:
I found the problem: "Mark Extreme Values" had been selected under the View menu.

[Gerhard Huber]

I think you have activated "Mark Extreme Values".