What commands appear gray instead of black in Excel?
Commands that are not relevant at a particular time will be
greyed out. For example, before you do a Paste, you must first have
done a Copy or a Cut. If you haven't done either of those, then
Paste will be greyed out. Once you Copy or Cut something, then
Paste will become black and you can use it. If you have not done
anything, then you cannot do an Undo, so it is greyed out. Redo
will be greyed out until you have done an Undo. The same applies to
many other commands. So commands will be grey or black, depending
on what else you have done.