Do you have another monitor and/or cable to try, perhaps even a LED TV? Those colored spots aren't like any artifacts I've seen before...
Generally, if your power supply is adequate and you drivers are up to date you shouldn't have any visual anomalies. Artifacts are typically described as being smaller pixel-sized patterns or groups that can change color and flicker as the GPU tries to render the frames.
This is interesting.... i have a pair of HD7970's in crossfire which have been experiencing a similar issue.
I just put it down to a faulty card, but i'm now thinking this is a driver issue..