Here's how I color code my tables: I have a large blue plastic bin on each
table which holds scissors, erasers and pencils. I tied a tiny piece
(4 -5") of yarn - each piece a different color - around the handle of each
bin. I tied a tied little knot. Maybe I'm just lucky, but so far, no child
has ever removed the yarn. Occasionally the bins at the tables get
switched. The children don't like this and they always change them or tell
me about it.