They are not bright enough by any means. When i attempted to make it show up better it then created little wrinkles in my brand new, awesome Bible. I wish I didn't try it out on one of my favorite verses.
I searched a long time for a bright, colorfast yellow. I saw this and took a chance --and I am glad I did! Highlighter goes on smoothly and doesn't crumple or rip delicate paper, doesn't bleed and stays bright. Love that it uses refills instead of having to buy a new marker each time. A+++++