I like to use different colors of ink to make my tasks and appointments stand out on my planner pages. I started out with a pretty basic color system using a Bic 4 color pen and used the colors as such:
Black: most things
Red: Important things
Green: Health/ exercise
But for some reason, 4 colors weren't enough so I branched out. I invested in some Sakura Micron pens, because they are archival quality. I keep my planners forever as a record of my life so I figured I'd better get some pens with ink that will stand the test of time. The Microns, with their archival security and vast color selection, are pretty addictive. They practically encourage chromatic diversification. So now my colors have expanded to:
Black: normal tasks and appointments
Dark blue: travel
Light blue: my husband (things I need him to do, remind him of, etc)
Green: Health/ exercise, and also money (when underlined with red)
Red: Important/ urgent items
Purple: my own personal stuff (purple is my favorite color)
Orange: kids' activities
Yes this may be a little excessive. But all the colors make my page look really good, and makes things stand out. And maybe most usefully, when I look back in my book to reference something it's easy to find. For example, when I need to see my workouts from last week, I only look at green colored items. This really helps when I'm looking at pages chock-full of writing.
Do you use colors in your planner? Do you have a specific color scheme, or just like things to look colorful in your book? What pens do you like to use in your planner?