Does the color of fishing line's matters ? I got a a roll of 770 meter/840 yards of red/orange fishing line, is it suitable to fishing with it alone, without a diffrent line attached on the "business" part of the line ? Would be nice to know before i pack it in mine kits. If you can't i asume you CAN use it as the main line for a nightline, right ?

To my experience the color only matters in very clear water when people play catch and release. For a while I used a line in neon yellow because it was easier to see for me. It had no impact on my results.
When you try to let the bait float on the surface it´s important that the last few inches of the line submerge. Otherwise there´ll be a considerable shadow which might warn the fish.

I reccomend a braided dacron fishing line for these reasons...
Monofilament line has "memory", meaning it will coil up on you when you unwind it and makes primitive fishing difficult.
Monofilament can cause nasty cuts if you happen to yank on it for whatever reason.
Those new "super lines" are EXTEMELY abrasive and can cut you to the bone if your not careful. I've seen it happen.
(Plus the abrasiveness is hell on rod guides and reels)
You can get braided dacron in multi-color. Which helps to camoflage the line.
And you can use it for other stuff.
But, red is one of the first colors in the spectrum to "disappear" under water.
Or you could use fluorocarbon line line which is clear and is supposed to be "invisible" to fish.