If you really have to have a red trigger - CMC Triggers AR-15 Drop-in Single Stage Trigger Group, 3.5lb Pull Weight

I got it to add to a black gun with red everything else. I have had many and have many CMC triggers and its the best cartridge style trigger you can buy. the manufacturer has the QC in there court. two part triggers even the best are slave to the lower hole geometry.so it can make even Geiselle trigger bad if the pin hole geometry is not exact. they have no control. this is the first time I got a CMC flat trigger that was not exactly 3.5lbs at center pull. mine is 2.8lbs and 4lbs at top and 1.5 at tip. pulled with a good trigger scale.