SG - this is how I did it... note that this definitely works on CC2 Pro, dunno about CC3.
OK, there are a shedload of layers in a CC2 map. The important one for the grid point of view is "HEX/SQUARE GRID". Make this your active layer, and freeze and hide all other layers. You should now only see the hex grid.
Click the "Change Colour" icon (left hand icon bar), then select the entire hex grid in the drawing area (I find clicking outside the grid, andthen dragging the clicked mouse over the grid most effective). Then click the colour you want in the left hand colour bar.
New hex grid colour.
Repeat as required until satisfied.