General Pastel Chalk Pencils - the white ones
These pencils are probably my favorite for marking anything that the white will show on.
The marks usually rub away.
The down side of them:
1) they do get dull quickly - I've found that an eyebrow pencil sharpener works as well as anything to sharpen them.
2) Occasionally the chalk in the inside of the pencil breaks and then it is impossible to sharpen it. May as well throw the pencil away.
I do occasionally use a yellow or gray one - the gray is generally hard to see., but I am more comfortable using the gray on a white fabric than the yellow one.
I do have a couple of yellow ones, but do not use them very often. Yellow marks can be very difficult to remove.
General does make these pencils in assorted colors - but I do not have them, so have not used them.