The notification LED is on the front face, upper left corner hidden among the black bezel. It's to the left of the ear piece speaker grill. You can't tell it's there if it's not on, and it only glows two colors - a very faint green and a brighter red.
The red color is used for charging, and the green light can be used for notifications. If you try to tell your application to use some other color besides white or green, the light just won't turn on. I tried it with K-9 Mail and the only way I can see the light is to set it to "white" and only then it shows up as green.
It's so faint, I have a hard time seeing it in bright daylight. Indoors it's fine, but it certainly won't get my attention unless I'm looking for it.
It's a great phone, by the way. Just don't get it for the LED notification. It's okay, but others are better and brighter.