Hi! Just FYI, I am using a Wacom Cintiq 16, so it might just be the device reacting to Krita.
I do not know if other tablet’s react the same way, but if you have this same problem this may just fix it like it did for me.
I recently had a problem where I would chose a color, but when I went to paint it, it came out as another color. For example, I chose Turquoise but when I started painting the color showed up as a greenish-brown on the paper while the color indicator still showed Turquoise.
Thanks to AhabGreybeard it was finally solved! I changed it from direct 3D to open GL and it seems to be working well! I admit that I am very very very new to working in the digital art world so I am going to quote what AhabGreybeard instructed me to do.
I hope this helps