Signs that don't face a certain direction are darker then usual

Hi there, I'm having a problem for as long as I can remember. Signs that don't point to a certain direction (I think west) turn wird and different than signs that do face west. (See picture)

So if I see any sign that doesn't face the right direction, it turns this wird color. How can I fix this? Or is this a bug.

PS: I'm the only one of my friends that is having this problem...
PS 2: The colors in the signs are exactly the same: line 1: Bold/White, line 2: White, line 3: Normal (black), line 4: Aqua / Light Blue