There is no way to create a light source with the drop command. You can only config one via an addon; basically you can make a custom fireplace, and make it glow whatever color you want, however bright you want. But again, you CANNOT do that via scripting.
Now, the color format for the drop command is in RGBA format. That is a very standard format for computers, and it works like this: each slot in the array is the amount of red, green, blue, or alpha (transparency) in your color. OFP makes it easy, because you are just doing percents (0-1). Usually RGBA uses numbers from 0 to 255 (255 = largest 8-bit number).
Since this format is so standard, you can just search Google for "RGBA chart" or "RGBA picker" or something like that. You should get tons of results.
Just remember, the charts are likely going to be using numbers from 0-255, instead of from 0-1. This just means you're going to bust out your crazy math skills to convert
.