The number indicates the size of the LED, 0603 tells you it's 0.06"x0.03" big. a 1206 would be 0.12"x0.06.
Now the Power LED is a double-LED, why do you think it can generate two colors...it's basicly two LEDs in one housing, that's why it's also bigger.
Oh and if you can't even see it under a magnifying glass you should uhm...get one that doesn't just do 2x but 4x, making it even bigger...