It’s worth mentioning that very young writers might benefit from using color when they draw. Thin colored markers allow them to draw with detail, while thicker markers or crayons provide other advantages. If you teach emergent writers (who mostly draw during writing workshop) then you might want to stick with something in color while they are in the scribbling stage, until they can draw representationally. Sometimes the only thing that helps kids remember what they drew is the color (as in, the blue reminds them that it was a story about swimming in the water, the red reminds them of the pool toy they were playing with). However, once children are drawing representationally and no longer rely on the color to decipher the meaning of their pictures, you will probably find that they produce much more writing when they are not coloring everything in anymore. Many teachers put away the colored markers and crayons once kids are drawing representationally, and save the color for publishing at the end of a unit of study.
Another thing to consider is that older, more experienced writers are likely to be more fluent writers in general, and may not have any problems with erasing a quick letter or word here and there. If kids are using pencils, you might simply teach them not to spend too much time erasing—just draw a line through it if it’s more than a word or two. If erasing is an issue, some teachers snip the erasers off and provide separate erasers at the times of the day when kids might need them (math, for example). Some teachers use pens during writing workshop, but pencils at other parts of the day.
Ultimately, the decision is yours. To wrap things up, for fun, I hope you’ll participate in this quick little poll