The problem is on Calc.
- click on a cell to select it
- In the top menu, choose a background color for the cell (you can choose the font color or the background of the cell). Normally, when you select a color, the cell is colored instantly.
The "bug" :
When I use the OMG Gtk+ theme, the color cell don't change when I select a background color.
If I double-click on the cell to edit it, the color appear, but if I quit the cell, the color disappear.
If I replace the OMG theme by Adwaita, the cells colors appear.