When I click on the "T" symbol with the drop labled with "IRC-Color", then not changing anything and clicking "OK" a string "%C01" is added in the chat input field. I'm using german as language so lables could slightly differ.
Yes... don't see the problem with that as that is what is set in the dialog by default. What did you expect to happen?
I'd expect nothing to be added into the chat input field. There simply shouldn't happen anything.
The box has a default item selected, and a cancel button. This is correct behaviour.