These are the most amazing pens I've encountered. I like to draw in pen, namely because it looks sharper, and erasable pens usually suck. BUT these erase with friction (both in gel and marker pen style), leaving NO trace, and no eraser shavings. It erases better than pencils and doesn't smudge during use. I'm smitten.
Color coding - something I said on another pin I would do. I like to see how others do it, though. If you think you might want to change color code, use a sticky note at the beginning of each section/month/week so you know what your code was before, then put your new color-code sticky note at the beginning of where you made the change.