Sorry for my ignorance guys, You were right I placed it in a standard module.
Now that I placed it in the right place it still doesn't work properly.

Like I mentioned in my first post sheet2 contains formulas which retrieve information from sheet1. it is in sheet1 where I update the cells. But the color of the cells on sheet2 should change.

I placed both the code I mentioned in my first post and your code separately in the sheet-code and made a button which triggers your code.

When I enter a "V" on sheet2 and press the button the color of the cell is changed indeed. But as I mentioned already sheet2 only contains formulas