A dark colored grout, but it has to be done very carefully and the joints cleaned and shaped to make thinner grout lines than typical.

Wow, Kathy, I think I'm as impressed with your "can do" attitude and common sense as your impressive kitchen redo. Thanks so much for sharing. Love all your color sections, especially the way the fabric in your kitchen window curtain pulls it all together. Before, the kitchen was chaotic, and now your colors are so soothing. Also love the way you rearranged the cabinets to maximize your space and storage. By the way, I know what you mean about measuring as that scares me too when I'm spending real money. I do have two suggestions for when you save up more $$$. The first is that you order full extension drawers, or trays, to go inside the large base cabinet with the double doors on the right side of the range. I ordered from Quikdrawers.com for the cabinets in my dining room and am extremely happy with the company and the result. They make a quality product, the guy who helps you (Keith) knows his stuff, and spacing between the trays is fully adjustable to maximize storage for what works best for you. Those pull outs certainly beat standing on your head and rearranging to see what's in the back. The second suggestion is to add a light rail and led puck lights run by batteries that you can just tap to get them to come on. My daughter-in-law knows a number of her neighbors who have used that approach and that it works pretty well if you don't want to go the electrician route. Those lights should be available at the big box stores or online elsewhere. Again, five stars on your project all the way around. It is well worth all the time, stress, and worry. Also, your low budget is hard to believe.

Since the cracks are purely cosmetic you can use caulk to cosmetically fill the cracks. Do a small test to make sure the caulk visually meets your goal.

Do you really want the grout to be a feature? I'd go with the closest match to the tile, which is either the top or the bottom. If this is supposed to look like wood (can't tell from this small piece), then it's especially important that it not really appear to have grout, or the illusion is ruined.