Laptop screen shows colors tending to gray

Question

I have a Dell Precision 6600, under 16.04LTS. Sometimes I find that colors turn in general to somewhat gray (as it is now, and I cannot get out of this). Then, for some unknown reason, the screen comes back to normal.

Checking pure white (FFFFFF) for instance shows as gray, in any application. I tried answers here:

How do I adjust the screen contrast?

Script to display all terminal colors

What can I do to solve this? A reboot (or even a logout) possibly solves this, but I mean to identify the cause and solve it without logging out.

Answer 1

I had several windows from screenshots open. Each of them lightly shifted colors towards gray, with the result being a noticeable change. Closing each one of them gradually removed that tendency, finally leading to a "healthy" image.