All the pictures are from the print-outs in my binder of Colossians.
I always underline the author of the epistle in blue.
...the Spirit is the left corner (with a cloud).
The recipients are underlined in orange.
Boxes, circles, and other geometric shapes are great choices.
I used a small stop-sign symbol in red with a "W" for warnings. The blue boxes are commands and instructions.
Finally, I used a green box marking for Gospel. You can see I marked synonyms and pronouns the same way.
**For a complete look at how to mark your Bible, see my page here.
If you are having trouble remembering your markings, use an index card or create a separate binder page to catalog the markings.