Blue- If It happens it happens. This is a situation where you are attracted to someone but you wouldn't make a move but if they did then you would go with it.
Green- Go for it. This is when you are attracted to this person and you want to pursue. It also works for when you see someone and think they are attractive but you don't know anything else about them.
Yellow- is caution. When a situation was formerly green and something about this person causes caution to the pursuer.
Orange- Is very cautionary. There is very little reason to continue pursuing this person. There is something that is wrong with them, or they don't get along with you or the people that you are around.
Red- Get out of there. This could be someone that is unattractive or just full blown crazy and you should have nothing to do with them. Cut off all communication get out of the situation.
If you can't get a good view of a someone you can ask for a color from "The Color System" on how hot they are.