I have loaded a lot of 45 Colt loads and most times it's with a 250/255gr lead bullet.
I have used W231/HP-38, Clays, Red Dot, AA#5, Universal, Unique, HS-6 and I think Herco too and a few other. More recently when looking for a light load I tested two favorites in the 45 Colt, W231, Red Dot and added Trail Boss for the first time.
Currently my favorite "normal" load is a Missouri Bullets 250gr LRN and 255gr LSWC bullet over 10.5gr HS-6 with a WLP primer.
My light 45 Colt load is a Missouri Bullets 250gr LRN bullet over 5.6gr Trail Boss.
My new Cowboy Action type load is a Missouri Bullets 200gr RNFP bullet also over 5.6gr Trail Boss.
If you can't find Trail Boss you can try Clays (I know, too hard to find too) or try to find Red Dot, PB or Promo. All will make good light 45 Colt Cowboy Action loads with the starting charge weights. Using a lighter 200gr bullet will also reduce the felt recoil and muzzle flip.