XTREE enhancement: New special color index code "=" may be used wherever an RGB color index is used (such as to specify the background color in a cell) to reset the color back to the default. In most cases, this is no different than using a space, with the main exception being that when re-entering an editable tree, a color index of space is interpreted as meaning you want to preserve the current color (whatever it is), whereas "=" will reset it back to the default. This issue arises primarily when using XTF_NOREDRAW and XTROP_RESELECT, where XTREE avoids re-coloring anything except the editable cells with non-blank color index codes.
Note that previously you could have accomplished the same thing by explicitly defining an RGB value of 0,0,0 (which is interpreted as "default color", rather than black) and specifying the associated index value. So the new mechanism is just a shortcut (avoids the need to define an extra RGB index, and standardizes the code so as to improve clarity).
THERE ARE NO REMAINING DOC ISSUES AFTER THIS
