Review the use of the entities currently used to indicate sameness or difference of related elements.

X could be replaced by some form of delta, for "modified"

A left-arrow or right-arrow could be used to indicate whether an item is only in one API or the other, in a 2-way diff.

Also, review the use of colors, for accessibility reasons. (At a minimum they should be user-settable in a stylesheet, and documented as such.)