Grid cell value loose alignment when color is set

I set HorzAlignment of a column in the grid to gtaCenter. text is perfect centered. Then I set the background color via the grid.colors[c,r], the color is set, but the alignment is gone and the text is now left aligned.

How can I get it working? I seed to set the background color of a complete row, depending of the data, but all column alignments are gone after doing that.

Please use HorzAlign[c, r] for horizontal alignment.