runway signs

[White Owl]

I see signs placed along runways, and I wonder what exactly do they mean? We have black and white striped, red and white striped, solid white, and solid yellow. The game seems to automatically place yellow signs along the currently active runway, but what are the other colors for? When you're placing static objects on an airfield, trying to keep semi-historically accurate, how do you decide which runway signs to use where?