There are 4 different kinds of runes:
Marks(Red)
Seals(Yellow)
Glyphs(Blue)
and Quints(Purple, but generally just called quints)
Marks are primarily offense-oriented, Seals are Defense and Glyphs are magic, with Quints just being very strong runes, but you only get three instead of 9 like the others.
Also, you can, for instance, get some defensive stats on Reds, but the effect is significantly less than if you bought the same effect in Yellow.
Marks(Red)
Seals(Yellow)
Glyphs(Blue)
and Quints(Purple, but generally just called quints)
Marks are primarily offense-oriented, Seals are Defense and Glyphs are magic, with Quints just being very strong runes, but you only get three instead of 9 like the others.
Also, you can, for instance, get some defensive stats on Reds, but the effect is significantly less than if you bought the same effect in Yellow.
A man in a wheelchair with a rocket launcher can make a big explosion once, then he's as weak as any other cripple.
-Some dude on the SWTor Forums
-Some dude on the SWTor Forums