How I mark my bible...

Marking prophecies of Christ: I underline the scripture with purple and a cross beside it. I use purple to underline anything about the Godhead in scripture.

As you can see in the second picture, I put a purple square around the verse with the prophecy and write next to them the scripture where the prophecy is at.
Scriptures of prayer/praise:, I highlight the chapter in orange and then the specific scripture numbers in orange,

Holy Spirit moments: I just started doing this but when I feel the Holy Spirit strongly while reading scripture, I now mark the verse number with a cloud around it with purple, same color used to underline things about God.

Color coded highlighting: This is great for going back and looking up scripture.

Blue=Promises
Pink=Love/Discipleship
Orange=Faith
Green=Family
Yellow=Salvation
Purple underline=the God head

In my previous bible I used a different color code, as follows:
Pink=Commands/Instructions
Purple=God's Character
Yellow=Prophecy
Blue=Promises
I used crayola twistables to highlight so I highlighted the purple but I prefer to underline the purple because sometimes the scripture can be about God and faith or another subject.

Scripture I memorize: I put a half square type bracket at the beginning and the end of the scripture I have memorized or have on my memorization list.

Scripture I love: I put a pink heart beside my favorite verses.        

Scriptures I underline and circle: I underline everything related to God, Jesus Christ and the Holy Spirit in purple. I square traits of the Godhead or things that they do/have done.

I circle things we should do as Christians or commands in pink (same color I highlight love/discipleship in it).
I underline all things we should avoid such as sin and satan in red.

                                                        

General Information: I mostly use this in the gospels,  the Torah and books of history (such as 1 Kings). I underline all important people or highlights of the story in green.