I don't plan on purchasing any, but here's a photo that may help you decide on the color choices. From left to right: $5 Group Buy (
MSK), $100 Group Buy (Matsui), $5 GB, Majestic White (
MSK), $5 GB,
MSK Sample Red, $5 GB,
MSK Sample Green, $5 GB,
MSK Sample Yellow,
MSK Sample Black,
MSK Sample Blue,
MSK Sample Black.
My apologies for the flash reflection; I don't have what you might call camera skills. For that matter, I also lack touch up skills. In real life, the colors are not as bright as they appear under flash. From across the table, the white and yellow are most distinguishable from the black. The white is also easily distinguishable from the Matsui plaque. Funny enough, it is more easily distinguishable than the black $5 GB plaques are. The red is easy enough to distinguish as well, and the green and blue are each barely distinguishable. In average room lighting, dirty stacks with blue or green would be extremely hard to notice. With a reasonably bright flashlight shined on them, the blue is actually more distinguishable than the green. For what it's worth, I have fairly good color vision, but I imagine the results could vary significantly for those who are color vision deficient. I would be happy to take additional pictures if they would come in handy for design purposes. Hope this helps!
Oh yeah, one more thought.
MSK material has had some references to another configuration. If you can see in the picture, the "insides" are basically made up of five layers, for example white, green, green, green, white. The alternate configuration I've seen referenced would go white, green, white, green, white. I have no idea if they actually offer this configuration, as I haven't seen any plaques with it, but if it's available it could help to brighten up the blue and green. Good luck!