Well this is a really small bug that effects servers and regular singleplayer, and it is only the 1.8 clients that has the issue.
All the color signs that exists or is being placed in the directions south and north are discolored so you almost can't see some of the colors.
While all the signs in the directions west and east looks just fine.
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No, it's MC-33304. Here's a picture form that thread: https://bugs.mojang.com/secure/attachment/43105/2013-09-30_14.35.35.png
Duplicate of MC-33304