RoyHobbs, On the picture of the brown granite countertop, the back edge of the countertop (which was previously covered by the 4" backsplash) is lighter than the part of the countertop that was not previously covered by the 4" backsplash.

That lighter part is what the OP is asking about trying to darken to match the rest of the countertop.

I have used this product to darken my black granite that lightened around my sink from my hard water. I had to put on a couple coats to get it dark enough, but it worked. I was so happy because I thought my counters were ruined.

Thanks

@barncatz and @Cecelia Brandon - thanks for those explanations. I stared at the pic and could not figure it out!

@RoyHobbs, cannot tell you how often that happens to me on Houzz!

I am a fabricator. There is a product called "Ager" which will darken stone. That will work better than sealer which normally doesn't darken stone. Go to Granquartz.com; they have several products that might work for you.

The lighter section hasn't seen sunlight. I doubt an ager is going to do the trick, but who knows.