When a wall is colored in red in your design, this typically indicates that the wall isn't properly connected to the adjacent walls, resulting in an error. The wall turns red to show you which wall is causing the disconnect. 
See example image:

This can happen in some rare cases when you for example click and drag a wall into a new location, where there are other connecting walls and they end up overlapping. 

This guide will help describe the steps on how to fix this.

1. Click the red wall to select it.
   It will get a blue outline to show that it's selected. 
2. Delete it. 
   You can either click on the trashcan in the blue shortcut menu, or press Delete on your keyboard.
3. Draw in a new wall in its place.

Top tip! You can adjust the thickness of the wall before, or after, you draw it! Learn more here: Create Thick and Thin Walls

Should you need any further assistance, please reach out to our friendly Customer Service via email to support@roomsketcher.com.
Remember to include the name of the project so that they can easily identify the wall.