There's lots of roulettes that are relatively common that aren't listed in the TCR. It comes down to that unless somebody notifies them of the color, mold etc, they often times don't list every roulette in every color.

Also...that said, there's other reasons too that this can happen:

An issue with color description can often times lead to a chip being lised as an incorrect color. Scans don't always represent the true color, and unless people are using the Paulson color chart, they can mis-describe the color.

Some good examples of this are white when the chips is off white, or or even tan or beige.
Another example is ochre vs mustard. Pink or purple vs fushia, and on and on.

Then we have the occurance of faded chips.