I created an RGB bitmap image in Photoshop at 256x256 pixels (top image).  Using all straight lines, I drew 127 lines of red, decreasing the color value by one for each line.  Then I copied the layer three times, rotating each layer as needed.  I then changed the color-channel output of each layer to get green, blue, and gray.

 

This was fine for the website (www.jwartistry.com), but I needed to create a higher-resolution image for print.  So first I picked up the challenge of using Illustrator for the first time.  After finally getting the hang of it, and learning how to use gradients (first time as well), I created the vector image in CMYK (middle image).

 

Wanting options, I then turned back to Photoshop and, using my new knowledge of gradients, created a new RGB bitmap image at 2400x2400 pixels (bottom image.)  End the end, though, I decided to go with the vector image created in Illustrator.  It looks cleaner, crisper, and scales easily to any size.