Interior colour issue UE4

Hello people!

First of all, thank you for taking the time to read my post.

I’m fairly new to UE4 and trying to make some interior designs in UE.
At the moment i’m having an issue where all my fronts of the kitchen are showing in a different colour. (see the picture I’ve enclosured)
I have no idea how this is happening?

Hope some one is able to help me out!

With thanks in advance.