Why is this color difference happening? Can it be prevented?

Greetings,

I am trying to put 2 rounded rectangle meshes together to make a corner. However for some reason even tho they are exactly the same Y position the point where they join is very obvious because there is a noticable color difference despite it being the same mesh just cloned with ctrl+d. I am unsure if this is roblox or my brain because i know there are some optical illusions that rely on the brain changing the shading of objects for a better 3d visualization of space.
Hopefully there is some way to fix this that doesn’t involve me making a new corner mesh every time i need it.

Thank you for your time

It’s the way the mesh is shaded to appear rounded.
If both are the exact same and are crossed over at the corner just tilt both of them .1 degree inward so the intersection line meets at the 45 degree angle like the inner radius does.