> It's a highly unstable particle made of 4 quarks, kind of like a meson (which is a quark/antiquark pair).

I thought the new particles were cool because they don't follow the color charge analogy, whereas mesons do follow the analogy?

The posible colors combinations of the mesons are red+antired, blue+antiblue and green+antigreen. The color+anticolor are not fixed, they “constantly” change. (Actually, any linear combination of the pairs is posible.) http://en.wikipedia.org/wiki/Quark#Strong_interaction_and_co...

There are some abstract algebraic properties of the particles and these properties produce the color rules.

With 4 quarks the only possibility is a mix of 2 quarks (with colors) and 2 antiquarks (with anticolors). For example red+antired+blue+antiblue.