I looked at the sticker and can't really figure out how to read the color.
It just look like a dark blue plastic lens to me.
Can you tell me how to read, I think it may need some extra water topped off after a few years now.

 

The water just has to be higher than the lead plates. If you pop off the tab and can see plates above water, then add some distilled water. If not, then it's high enough. Be careful too, that's sulphuric acid, it will burn your skin(my friend messed up his face when it splashed on him).

If your water level is low though, chances are the sulphuric acid has made some kind of reaction with the plates and the surface of the plates have a coating of sulphate on them. You pretty much need a new battery at that point, summer months may be ok, but i wouldn't trust it in the winter. At least carry a set of jumper cables in your car.

 

pop the caps off the battery. look down the hole and you'll see two prongs extend toward the acid. if the water level is below the prongs, then you'll need to add distilled water. you add water until the meniscus of the water hits those prongs...then you'll see the meniscus "flip"...that's all the water you need. do that for each cell. I usually use a water bottle with a very small hole drilled in the cap... Like gggplaya said, be careful. I've ruined plenty of pants to battery acid.