Unity Editor Skin color bugged?

Hi, since today i have a problem with my Unity Editor Skin.
Normally, everything is colored in a light grey.
My Editor is very dark right now. Although i have chosen the “personal” skin, not the dark “professional” skin). This Problem is only in one Project. If i load another Project, the colors of the skin are correct.
Does anyone know how to fix this? Thank you

Bugged-Personal-Skin: Screenshot by Lightshot
Correct-Personal-Skin: Screenshot by Lightshot

It’s a bit late, but maybe my tip can help someone. I had similar problem with the professional skin after switching from 2017 version to 2018.

The problem was in Standard Assets folder.
I deleted Standard Assets/Builtin Shaders/DefaultResourcesExtra/Internal-GUITextureClip.shader and all my editor windows became pink. Then I reopen Unity and all was fine with the skin.

Update: it seems that actually there is needed to remove the whole Builtin Shaders folder from Standard Assets