Hi Maximilian,
Since you need a helper column anyway to use the colors, I would
tend to just put some meaningful letter/number/text in that column
and filtering would be more meaningful if you wanted to filter on
different values.
But there is nothing wrong with Chip's solution and did not mean
to imply that there was. In fact I hadn't seen his earlier posting
before I posted. The advantage of User Defined Functions
and Macros is that you can get Excel to do more of what you want.
So if you already have things color coded then obviously that is the
easiest way for you to work with your data. If more than one user
is involved, many might prefer to use the keyboard then using the
mouse. Others might find reading data with red background annoying.
Your bump with another way to mark the cell with data in it leaves
only shading which would be worse.