It's the gray platform that intersects the middle of the 456 and the end of the NQRW

That's confusing. I wonder why it's rendered that way. (Though I feel kind of bad about complaining.)

Because the NYC Subway "color" of the L line is gray! It's logo is a gray circle with a white "L" in the middle in a sans-serif block font.

Yeah, though also the other two tunnels seem to be shown with much wider colored strips. The L looks here more like a walkway between them.