You can't tell anything from looking at the LED, the color comes when the device is activated. The LED's housing is clear. Some of the older, first generation ones used a tinted plastic housing to produce the color since they hadn't learned how to produce color yet.
Without getting all scientific, it has to do with the frequency of the light being produced and how it is filtered by the red plastic lens.
Yes that's what happens. With LED's the red lens blocks, or absorbs part of the light, but if the bulb is red, the lens doesn't filter out that spectrum of light.. You can google it for a better explanation.
