Could it have something to do with pixel snapping?
Cameron MacFarland
2008-11-18 11:49:00
Are they in a grid? It could be related to http://stackoverflow.com/questions/267364/wpf-eliminate-transparency-between-grid-cells#267954 which we never really resolved.
You could ask one of your tech-savvy users to run Snoop while the problem is showing, then:
This will tell you exactly what control is producing the color you are seeing in the artifact, which may be a big clue in fixing it.