Here's a pretty good photo I found of Malayan shrimp sporting its "typical" color you'd most likely see at the store:
http://www.aquajapan.com/encyc/shrim...na/sp0002.html
If you look closely and compare it to the photo of an Amano shrimp, they look VERY different. HOWEVER, Amano shrimp are usually sold while they are still in a "juvenile" stage, so their distinct patterns and such are not so obvious. When the Malayan shrimp are still showing this lighter beige color, it's fairly easy to get them confused with Amanos if one is not paying attention. Size and color are often very similar.
Here is what Malayan shrimp can look like when they feel "at home":
http://www.wirbellose.de/arten.cgi?a...&artNo=029
As you can see, they can take on all sorts of colors. They're a lot like rainbow shrimp, only bigger and I believe they hatch larvae like Amanos, whereas rainbow shrimp hatch just smaller versions of themselves, like most Neocaridina species I know of.
Note the characteristic stripe that runs down the carapace of the Malayan shrimp. See how at approximately half-way, this stripe sort of "bleeds" to the side. This stripe feature is usually apparent no matter what color the shrimp. Amano shrimp also can have a line going down the same part of the carapace, but it's much thinner. They also have distinct spots and dashes that run along the sides, which Malayans don't.
-Naomi