For some people the first image to pop into their heads at the mention of color is a rainbow, for me it's stained glass windows. I especially love the two featured above. The first is by German artist Gerhard Richter who created the window to replace the cathedral's original, which was destroyed beyond repair in WWII. The second window is from the Thanksgiving Square Cathedral in Dallas, Texas and was photographed by flickr user shawnoconnell23.
(Found via anArchitecture and Something Seen)