Different colors for different categories?

Hi
Is it possible to display different colours for different categories in the calendar. (latest version of calendar and WP)
ie. if i have 2 categories.
Events 1 = Red background black font
Events 2 = Blue background white font

So its easy for viewers to separate the categories?
Or is there another way to filter categories?

Im OK with CSS, but would need and php code explaing if possible.
Any help much appreciated