My horse fits a semi quater horse bar western saddle what is that in an english saddle?
As most people have said, it depends on the shape of your horse and the saddle brand. But typically a semi-QH bar western saddle will be similar to a medium or narrow tree english saddle. But not always. A lot of tack stores, including some online are willing to let you "test ride" a saddle, where you would get to try it on your horse and see what you think of it and then buy one if you so choose. This might be a good option for you. Also, some places will let you trailer your horse into the tack store, where they will try on saddles and tell you which one is the best fit. Make sure that if you have a professional fitter come that you let them know what your budget is and exactly what you are looking for. Most come with some pretty hefty priced saddles.
My saddle has a 16in seat what would that be an english saddle?
Again, I'd look into some saddles, maybe go to a tack store and see what you find is your preference. Typically, a 16" western transfers to an 18" english.
What leather colour? I am planning to just stay with english pleasure and MAYBE jumping but that's up in the air right now.
I'd just go with a medium brown/havana brown. They match all horses and it doesn't go out of style. I personally like to stay away from black saddles, unless using it for dressage because they just don't seem to fit in english pleasure, and I haven't seen many for jumping, either.
Any brands to stay away from and others to keep in mind?
Depending on your price range, wintecs CAN be good for some horses. They do have the options of changing the gullets, but like many other saddles, the gullets don't always fit your horse as well as you'd like. These are also synthetic so that's a preference thing. If you like the idea of the changing gullet but like leather, I'd look into Bates saddles, as they are the same thing only leather and more expensive. I've heard many people have good luck with passoa, courbette, stubben, and on the cheaper end, HDR saddles. I'd stay away from the cheap-y brands like silver fox, cortina, all of the ones you will find really inexpensive.
For english pleasure and dabbling into jumping, I'd look into getting an all purpose style saddle because it will be best for the different purposes. You could get a jumping saddle or a close contact if you prefered, though. Just know that if you get a jumping saddle, the best ones have the block at the back of the leg, and that's not a typical thing that you see in english pleasure saddles.
Also pay attention to how it sits on your horse's back. I have issues fitting saddles to my horse because she has a narrow wither and a wide back which is typical for warmbloods. Because of this, a medium/narrow gullet fits her fantastic in the front and terribly in the back. There are certain brands that fit differently in different places and all horses are slightly different so I think it's just a matter of finding the right brand and right saddle for you.
In my experience, people may correct me as I'm not a perfect saddle fitter, with an english saddle, you want it to sit flat on the horse's back comfortably. This will typically mean that the back of the seat is about an inch higher up that the very front of the saddle when it's sitting on your horse. You also don't want to feel uneven pressure if you stick your hand in between the saddle and the horse's wither. If it's uneven, it's pinching them somewhere. Another way to tell is if the horse is typically not girthy and you start to tighten the girth and he doesn't like it, it can be a sign that it's pinching. You can also ride in the saddle until the horse sweats and if it's a solid sweat, it's a good fit, if there are dry spots, it's pinching in those areas.