How I Mark My Bible // Jim Hamilton
I use a mechanical pencil, a set of colored pens, colored pencils, and occasionally a highlighter to note things. As I've done this over the years, I've developed a color code for key ideas:
Yellow (colored pencil) = anything notable, repeated words in the passage, etc.
Pink = knowing or fearing God/the Lord
Blue = references to faith, believing, piety, etc.
Red = anything notable, but particularly the actions the Lord himself does
Purple = references to royalty/kingship/the coming Messiah
Green = references to earlier Scripture, whether quotations or otherwise
Orange = references to God's glory or name