While y'all are on colors, could I get an opinion on these?

I feel like the ground might be a bit too saturated. I can't really tell, though.
A week late, but...
I'm seeing a bit of a clash between the walls and the floors.
Tan/brown is one of the most annoying colors to get right in this game. The original palette has an extreme red cast to its colors - the overworld's tan ground and brown rocks specifically. That's why I went through some 20-30 variations of my own desert palette to get it right (as in, the best match between a stand-alone palette, and one that matches the pre-existing palettes).
I see your tans/browns are leaning in that direction - a notable red cast that becomes stronger as the lighter colors transition to darker colors, and a blue cast that all but disappears by that point. That's totally fine, and perfectly in line with the original game.
By contrast, your floor tiles have a green cast - the upper ones, barely noticeably, but on the lower ones, it's just as strong as the red is on the tans/browns. For reference, your lightest tan has a red : green ratio of 1.1 : 1.0, while the brown by the upper floor has a 1.5 : 1.0 ratio, and the dark brown by the lower floor has a 1.66 : 1.0 ratio. However, the "gray" on the lower floor has a 1.0 : 1.4 red : green cast.
In other words, your lower floor leans as strongly toward green as your mid-walls lean toward red. Which, to me, gives the screen a subtle Christmas vibe. Probably not what you were going for 
So, I think the walls are upper floor are fine, but I'd tweak up that lower floor to ditch the green cast (along with the similarly strong blue), or just aim for another neutral gray like the upper floor.