Wierd Overworld texture

What I expected to happen was...:
The dead bush for Over world when you customize flatlands will stay normal

What actually happened was...:
The dead bush had a brownish background
Steps to Reproduce:
1. Click on "Create New World"
2. Click on world type unitll its in Flat Lands and click customize...
3. Scroll down slowly then when you begin to pass Overworld Button the brown Background appears