but perhaps one saving grace is that you have little to lose by being mildly noncompliant. So if your son's school is like ours, he can color quickly, use the extra time to read a book (I hope), and perhaps accept a slightly lower grades in 1st grade. If your school had a gifted program that depended on teacher nominations, the calculation could be different.
When DS was in PS in skipped 1st grade, the teachers mainly emphasized on coloring and cutting - 2 things that my DS was not good at and was absolutely disinterested in. He could color well if someone sat with him and instructed him. On his own, no way. He rushed through coloring (which was everyday) and went off to the Blocks and Lego corner of the class to build something which was more important to him than the unchallenging work.
At home, all the "fun coloring math" homework (color the pieces of the puzzle green where the sum of the numbers = 9 etc to figure out the hidden animal) were colored by me (my DS was doing 4th grade math and some pre algebra at that time that I did not care if he refused to color in pictures for math).
The flip side, as Bostonian says, is that the teacher would not accept that DS was ready for higher level acceleration because he did not perfect his coloring and cutting skills (he could do well with a few reminders to slow down and be neat). She said that he got frustrated if things took long and coloring a picture took too long for him. We pulled him out of that school and put him in a school with rigorous academics where there is very little coloring, cutting, pasting etc. Big relief for the whole family! My DS was just bored to death of coloring because he did a ton of it at daycare and preschool and he was ready to learn academics. His fine motor skills are excellent (he plays piano at a high level and builds circuits with small components for fun), but he hates coloring and using that as a standard for measuring a child's readiness for higher level work is stupidity.