All the particles that can be observed in the experiment are monochromatic. For example, if you put quarks in mesons:

Red->; blue

Blue->; green

Green->; red

It turns out that this meson has not changed, and it is still itself.

Of course, a single quark does not have this property, so it is not a color singlet, and certainly not an octet, but a triplet. Under the rotation like a plane, the three States of red, green and blue always change with each other.

Octet states have eight independent states under rotation, but the rotation here involves many quarks, which requires deep mathematics to understand, unlike the intuitive example above.

You can read some books on particle physics, group theory and group representation theory if you are interested. Of course, you have to study linear algebra or advanced algebra first.