In one of the books I have, the recommendation for Konica 750 is a deep orange (e.g. B&W #41). It has the advantage of being a lot brighter than 25A red or others. I use #41 almost exclusively with the Konica 750, and it works well for me. The Konica IR is kinda slow which is a typical good news/bad news. My base exposure is f11 @ 1/30 with the #41 and a bright landscape with lots of greenery.(posted 9100 days ago)The slowness of the film makes it (relatively) easy to handle, but makes a tripod desirable. I generally set the lens at the hyperfocal distance, bracket, and pray.
Good luck