As always, I'll preface that I am wildly undereducated, so i may be overlooking something or be completely unaware of another relevant property.

Color Confinement dictates that to "assemble" a baryon or meson it must be color neutral. Eg q -q, or qqq.

Looking at a proton it has a composition of uud. Let's say those quarks are charged r,g,b respectivley. What is the difference between these two up quarks that their color charge is different?

EDIT: As far as I know the color charge of a quark refers to the strength of the strong field on a given particle. If a quark changes from green to blue, how exactly does this quark experience the strong force differently?


1 Answer 1


Colour is independent of flavour. An up quark can be red, green or blue. Since gluons also carry colour, the colour of a quark isn't fixed. When a blue quark interacts with a green quark (of whatever flavour) they do so via a gluon that carries "blue-antigreen" (or green-antiblue) colour, and this has the effect of swapping their colours: The blue quark becomes green and the green quark becomes blue.

Colours are constantly changing, whereas flavours only change rarely (due to weak interactions) In a proton the quarks flavours are uud, but the colours of the up and down quarks are not fixed.

Apart from the change in colours, there are no consequences of a change in colour. A proton with a red down quark behaves exactly like a proton with a green or blue one

A red up quark relases a red-antigreen gluon, and becomes green. the green down quark takes the gluon and becomes red. Similar processes are repeated with the blue quark

Gif Animation from wikipedia

  • $\begingroup$ I'm aware that flavour and color charge are independant of one another, but what are the consequences of a pair of quarks exchanging colors? $\endgroup$
    – Stefan
    Oct 12, 2019 at 6:23
  • 1
    $\begingroup$ There are none. I've edited. $\endgroup$
    – James K
    Oct 12, 2019 at 6:40

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