Here you specify the Red, Green and Blue values for the color you want and the RGB function returns the proper number.
It's still not very easy to tell at a glance what the color is, but it's certainly easier than the first expression.
I wanted an easier way to specify a color. So I created a new function, f_color. You pass it one of the PowerBuilder color names and it will return the proper number. For example, our alternate row highlighting expression now becomes:
if (mod(getrow(), 2) = 0, f_color("White"), f_color("Gray"))
Plus, you can now do things like use Transparent and the Window colors:
if (mod(getrow(), 2) = 0, f_color("Transparent"), f_color("Button Face"))
I've made it available here. Just select File -> Download from the Google Docs page that appears.