@Egg, I've not had your difficulties.

I have Replace Colour set when I drop a colour from the Colour Bar.
The Options are Set Fill Colour, Set Text Background, Set Paragraph Border & Set Paragraph Background.
Text is poor for colour line drop so I use Shift+Colour Bar selection for Set Line Colour.

If you right-click on the Colour Bar you see all five options listed.

The main point to note is these also all apply to the Text Area within a Table Cell but application to one Cell affects all Table Cells.
The second point is you cannot change the Text Area edges' colours separately; this is the same for non-Table Texts.

The Table and Cells additionally have their own colour selections that currently bypass the Colour Bar.
I find this, with just Named Colours, frustratingly wrong-hatted.

There are defined zones where a colour drop could alter the Table Background, and at a pinch, the Cell Colour.

Taken together, Xara does not have a well-defined User Interface yet.

Acorn