[SergeNL]

Thank you, Sepulturalex! The trick Works! (almost)
Some additional information for others:

BSplayer Color Controls did not work at all with my video card ATI Radeon HD 4200, onboard video card on my ASUS motherboard M4A785TD-V. AMD Phenom II X4 925, quad core.
K-Lite Codec Pack and FFDshow (2004) installed.

What did NOT help? Reinstalling BSplayer. Upgrade to FFDshow version march 2010. Update ATI video drivers. (always rebooting the PC)

The complete installation was a clone of the installation on my previous PC (Nvidia video card), and there the Color Controls had always worked. (So they do work with FFDshow.)
The Color Controls never worked on my new PC, and it took me 2 hours, to find this post.

What does work?
Double click the red ATI Icon in the Systray (in the right below corner of your screen) That will start Catalyst Control Center (CCC).
Close Catalyst Control Center again. That’s all! (you don’t have to change anything)

After this, the BSplayer Color Controls keep working all day, whatever I do. You can open and close BSplayer. You can even close Catalyst Control Center completely. Etc.
But after restarting the PC, I have to open and close CCC again, Once..

I prevented the ATI Icon from starting with Windows, using TuneUp Utilities’ Startup Manager. But it didn’t help. I had to start Catalyst Control Center from the Startmenu and close it again, to get the Color Controls working.

I can’t experiment with Catalyst Control Center, because every time you start it, the Color Controls keep working. I do not wish to restart my PC at every time I change a setting, to find out if some different setting solves the problem completely?
But the current solution is do-able. Starting and closing CCC once a day is not a big deal.

BSplayer-Team: Complain at ATI! Ask for better drivers!
This is highly damaging to BS-player! The Color Controls are one of the best features. People may choose another player, if they don’t work! (VLC-player did not have the problem..) All my video’s are too black without them, so I would easily switch players.
And many thousands of satified BSplayer users may be in trouble now. ATI is a huge manufacturer. And the solution is hard to find.

Who is to blame? If the OS + All software supports Color Control, and the videocard does too, then the video-drivers are to blame.

Wishing the BSplayer-team a lot of fun, success, and sales..