That's an unfornate situation you have with the countertop, especially since the joint is in an area that is very noticeable. Applying sealer may not do anything with regards to the shade as it will only help seal and 'enhance' the existing shade. I would suggest calling a pro stone Refinisher to see if they can work on trying to get the shades of the 2 pieces to match by sanding the granite down and refinishing it to try to balance the 2 colors.

I've had granite installed twice and the joints have always blended in very well. I'm not sure if it's because of the work of the company or the type of granite I purchased, but most people wouldn't know it was 2 pieces unless they looked very closely. If this is a new install, I would talk to the company and see what they can do. I love the granite choice by the way :)

Wow, that is worth firing a fabricator for. I would not except that kind of work on any of my jobs. Yes, that is the same granite but what you are seeing is the color variation. Since the granite is polished you will not be able to enhance (or darken) the product. Previous remodeling jobs that we have worked and come across situations like this our tile installers used a sanding pad to remove the polished look, opening the pores in the stone and applied a wood stain to the granite. I would recommend you call a professional vs. trying to do it yourself. May just make thinks worse in the long run if you try...
Good luck!

Call them back on this one! That is not OK.

I agree they should have known better than to match slabs there. Call them and complain that is not acceptable ever!

This is really a mismatch of material..we have been in the stone work installation for 40 years and wouldnnever allow such a mis match of stone. I would have the fabricator the problem