If you wanna change the clock color, open the Cowon Clock folder (C:\Users\YourName\Documents\Rainmeter\Skins\Cowon Clock) and open either digitshours.png or digitsminutes.png with Photoshop or any software for pictures.
If you're using Photoshop, press Ctrl+U and change the color of your choice in the first section. If you're not using Photoshop, try to find the color balance in your software.
Save and reboot Rainmeter.
Unfortunately, even though the hours color is supposed to be white, it always appears gray on my computer, despite the changes