Can you help me with this question on highlighting?

Use a different color, and if you wish to highlight a section already highlighted, then use your color in the margin next to the section you want to note.

If the old highlighting is done in yellow, any other color used over the yellow will change the color and you’ll still be able to see the printing through it.

If it’s already highlighted, you could try taking a different color highlighter and boxing in the paragraphs or sections that you want to call attention to, and contine highlighting and in the same color that’s there, and boxing in with the contrasting color.

Use a different color. Or, alternatively you could resort to underlining which may be really time consuming.

Circle the important info to remember with a black magic marker. had this same problem with a book that had been used many times. the only way to tell the difference was the use of a black magic marker. worked for me.