When partial menus are enabled the items which have not been recently used are represented using a darker grey color on the left of the item (in the column where the icon appears).
However, when Partial Menus are disabled by choosing "Always Show Full Menus" the darker grey color still appears. The problem is that this could be un-intuitive for a user, it also looks untidy.
I have been able to modify the source code in order to achieve this effect by checking whether or not Partial Menus are being used (in MenuGrid.cs, line 1071, where style.Interior is changed for items which haven't recently been used).
Maybe this change could be incorporated into the next release.