Why overexposed in game?

Hello.
I have a problem with too much light / overexposed.
Everything looks like on the included screenshot. Each element - actors, floor tiles, backgrounds are overexposed. I also placed character sprite as a widget and it displays normally.
I think that probably on level there are no sources of light - or I am wrong and I cannot find them.

Someone could tell me, why is it happening?
Thanks for help.
character overexposed