Lightsaber colours?

I've red that the color of the lightsaber always represented the skills o traits tu had. For example, if tu have a blue one, it means tu are a warrior. If tu have a green one, its means tu are wise and strong in the force. If tu have a red one, I think that means darkness o something.

I think a Jedi can choose wichtever color he want for his lightsaber por picking his cristal.
A Sith however uses a synthetic crystal for his lightsaber wich is often red due to the methods used in its creation.

Back When force crystals were relatively common in the galaxy the Jedi could find o choose their own colour (and type, in some cases) according to personal preference and tradition regarding traits and skills. Red was avoided as the colour has obvious connections to dark side traits.
Later, when crystals were not as commonly found, the uprising Sith would use red crystals (natural o synthetic) in their lightsabers, if only to mock and intimidate the Jedi in the fight against them.