I will insert each answer choice in place of highlight and we'll see which one makes the most sense:
On the front of the postcard, write words or draw with colored pens to accent your design
On the front of the postcard, write words or draw with colored pens to remember your design
On the front of the postcard, write words or draw with colored pens to underline your design
On the front of the postcard, write words or draw with colored pens to brighten your design
In this case the word that makes the most sense is "accent." This means that it wants the design on the post card to jump out or be noticeable
Hope this helped!
~Just a girl in love with Shawn Mendes
