The Lower Left four walls. (The four mountains) in the darkfantasy outside A4 sheet in MV Triniity DLC Don't match their respective grounds brightness from A2 respectfully. (grass, dirt, sand, and snow) (snow is a bit harder to see)
that might be intentional, because those tiles in A4 are not ground but ceiling tiles - they have a special passability that helps to simulate a two-level-dungeon with the ground being the lower level and the ceiling/top of the walls being the upper level (and you'll need an override like a ladder-tile to move from one to the other)
It matches in MV's RTP because they made a different design choice than the people who made Trinity. Whether or not it's a good design choice is a completely different matter, but being different from MV doesn't prove anything. As a tileset artist I can guarantee that this is definitely not the type of thing that could happen by mistake, someone made a conscious choice to make it this way. The proof is that the walls of the dirt and the grass are the same color to each other, but the grass is darker while the dirt is lighter. If the differences were there due to some sort of error, it would have more consistency, either with each other or by having the walls get darker or lighter as well.
Got distracted... again. So now I'm on project.... 5? 6? I can't even remember off the top of my head how many plugins I have in the works. Though I blame the latest two on a coding youtuber I watch occasionally. He codes in C++ but walks through the process well enough that it inspires me to do similar things for JS plugins. So... blame him for my lack of activity. lol