Colored Texts on Signs

You can use JSON-Text to create colored text on signs:

blockdata ~ ~1 ~ {Text1:"{\"text\":\"Green\",\"color\":\"dark_green\"}",Text2:"{\"text\":\"Red\",\"color\":\"dark_red\"}",Text3:"{\"text\":\"Blue\",\"color\":\"blue\"}",Text4:"{\"text\":\"Yellow\",\"color\":\"yellow\"}"}

(Copy this in a command block and place a sign above it...)

This is not a bug.