The Color Plus replaced the Basic Color Display as the mid-entry level Apple monitor in late 1993. The BCD had come out earlier that year to essentially fill the 12" RGB's void, just as the Macintosh Color Display took over for the Hi-Res RGB at the high end.
The Performa Plus was a different display altogether. I remember it being bundled with the 4xx Performas in particular (and also saw it on at least one P600). This was the lowest of the low end. Think of the basic, entry-level PC clone monitors of the time (i.e. Packard Bell, Compaq) and you've got this washed-out display.
Essentially, Apple had the following display lines for <15" color displays before the multiscan displays of 1995:
VALUE LEADER: Performa Plus
ENTRY LEVEL: 12" RGB, BCM, Color Plus
HIGH END SMALL DISPLAY: Hi-Res RGB, MCD
The Performa Plus was a different display altogether. I remember it being bundled with the 4xx Performas in particular (and also saw it on at least one P600). This was the lowest of the low end. Think of the basic, entry-level PC clone monitors of the time (i.e. Packard Bell, Compaq) and you've got this washed-out display.
Essentially, Apple had the following display lines for <15" color displays before the multiscan displays of 1995:
VALUE LEADER: Performa Plus
ENTRY LEVEL: 12" RGB, BCM, Color Plus
HIGH END SMALL DISPLAY: Hi-Res RGB, MCD