First, I got the extensions and dip dyed them with Strawberry Lemonade koolaid. Then I took a photo. Then I dyed over that with Cherry koolaid (to see if it would darken the color). It did.
The problem is it's really hard to see it! But basically it turned an auburn color with the Strawberry Lemonade and a little bit of auburn/ burgundy with the Cherry koolaid. I hope you can actually see it. I tried to get the best lighting I could with these photos. Here is an edited picture to point out the color change:
Obviously, adding koolaid to brown hair is not going to change the fact that you still have brown hair. It's just going to add a tint of whatever color you used. You'd have to lighten your hair if you want it to show up more than this. The process of lightening hair may cause damage. It's really up to you if you want to do that. I would suggest trying a dip dye on your hair before lightening it, because you may be surprised to find that you like the color and then you wouldn't need to lighten your hair after all. These photos don't show the full extent of the color. If you are in the sun, you'll see a much more vibrant red color. It really depends on your shade of brown (how dark or light brown your hair is). Light brown will show the red a lot better; however, the red will still show up in other shades of brown, especially if you are in natural sunlight.
Remember that koolaid can be hard to get out of hair, so try my tips and do a strand test beforehand. I hope this helps anyone with brown hair who is interested in koolaid hair dye.