The different colors have very slightly different widths for dealing with stage collisions/interaction (hurtboxes are exactly the same). It manages to make a difference here and normal CF doesn't collide with the wall until later in the animation than the others, and when he does get adjusted by touching it it's enough to put him barely over the edge and so he falls.



This should give you an idea of how small of a difference it is and how they compare relative to one another (measured in DerpMeters):



Normal 1088

White . 1096

Blue .. 1097

Red ... 1099

Black . 1100

Green . 1102