I don't think there is a right answer in this case. It is what you like. But also FYI, as I posted in another thread, in the case of two tile jobs in my house, I wish I had gone darker for both since in both cases, the grout dried quite a bit lighter and "stood out" more than I wanted.
Probably different from your case here, since both my tile jobs were dark colored tiles.
Good luck.

p.s. I am a newbie and have no designer experience ...

It really depends on the look you want. I used white subway tile in my master bath and kitchen, but wanted slightly different looks, so used different grout.

In the master bath, I used "Snow White" grout for a more seamless look:

In kitchen, I used "Oyster Gray" for a bit more contrast:

love them both, mommytoty! and i'm so grateful for you posting both. i think for my kitchen, i'd like the seamless look.

Elizabeth
Go for the matching grout!
Beautiful tile and kitchen

Here's mine, with a closely matching grout color (alabaster?)

You see the pattern of the tiles, but it's a very uniform, inconspicuous look. A darker grout would have looked more like the untiled bit to the right