I am working on Lattice Quantum ChromoDynamics (LQCD), but let’s skip the Lattice part for now and allow me to explain a bit the QCD part of this subject.
Taken literally, it would mean “how the colours evolve in the quantum world”, but, spoiler, no actual colour “red” nor “purple” is involved in the subnuclear world. As I am already on it, what we see as colour in our world is nothing else than light with different frequencies. In the quantum world, though, the light is quantized: there is a number N of photons, but in our macroscopic world we don’t see this discretization as N is very, very large. But the photons are not the only particles around, there are a lot.

QCD is interested in only some of them called quarks: up, down, charm, strange, top and bottom, which interact among themselves thanks to the gluons, another kind of particle as well. Actually, the comparison with the light is quite befitting. The photons allows for the interaction between electrical charged particles. This charge is a number: +1, -1, and so on.

For QCD, instead, the charge is not simply a number: it is a vector, so a set of three numbers. Why did we decide to call these numbers “colours”? Well, as I wrote above, the particles carrying this charge are the quarks u, d, c, s, t, b. However, we cannot isolate these particles, we only see them inside of other particles, for instance protons and neutrons (containing uud and udd, respectively).

Neutrons and protons, however, do not carry this colour charge. After witnessing this property, scientists realized that there was some parallelism with colours: if you assume that one up is red, another is green and down is blue and you mix them together, the resulting particle, the proton, is white, so no colour!

Of course this is just a simplification, but physicists like to choose funny names based on similarities like this one.