To your questions: finding the colors you want at the vendor you want can be a challenge; I had to compromise, but you decide what's most important (can you switch vendor to get the color you want, but may lose choices in other areas, i.e., styles). Weddington Way is a company that is based online so may have more options than Amazon but built for online orders. I picked short dresses (hopefully more likely to be used again) and not strapless (less chance of wardrobe malfunctions) and that actually narrowed a lot of selections. It was important to me that it be something the girls liked, so I let them choose the style that is most flattering for their body (although I think mine are all going to be in the same dress). I didn't pay any attention to fabric.
I like the idea of the officiant in the multi colored dress so she stands out rather than dressing similar/same palette as the bridesmaids. In the end, I basically said here's my rules (color, length, straps), as long as it meets that, you pick. Good luck with working yours out! More detailed story of my specific experience below if anyone wants to read that much.

My experience: I picked David's Bridal for bridesmaids' dresses because I have bridesmaids in different states so they could go and do fittings and all of that wherever was convenient for them and not worry about dye lot numbers (I wanted to have all the same color). The other nice thing about DB is they're the same company as Men's Warehouse so the groomsmen can match to any of their colors. I wanted to have something that my girls felt like they would be able to wear again so decided on cocktail length. I went back and forth on whether they should all have the same dress, but finally settled on each being able to pick their own style as long as they had the same color, were the shorter length and not strapless (I didn't want to have them constantly pulling up the dress to avoid wardrobe malfunctions, and no one argued about it). Had gone in the past with my NY maid (future SIL) and kind of settled on a dark green (fitting with wedding colors of forest/hunter green and silver). Options were still being considered so didn't get anything that day. Went in January with my MN maids and the dark green had been discontinued and I didn't like any of the other greens in the DB collection (their Vera Wang collection had the perfect color, but basically no selection for short and not strapless), so ended up with a grey/silver color. And after my churning about letting them pick their own styles, they picked the same dress! Go figure. So I told my NY maid she could match them or pick something different (to be fair); I think she is planning to get the same style as them. I also got a lot of questions about shoes. I told them silver, but they'll all be different. Not a major thing to me.

What's the etiquette on paying for bridesmaids dresses? I gave mine the colours and we consulted on what's app and they've chosen dresses and seem to be paying for the themselves, I should offer right?

I don't think there's any expectation for a bride to pay for bridesmaid dresses (unless you're insisting on something super expensive, in which case it's a nice gesture to at least offer to help out).

I think the traditional gift is the jewelry. So, you could switch it and give the dress and then they're responsible for their own jewelry like Marla Jean if you wanted to pick up the dress tab. I'm planning to give my girls the jewelry.

I have gone down the path of paying for the girls dresses, hair, makeup, jewellery and some other gifts on the days - a robe & clutch to use.

I was going to cover the shoes as well, but there was some issues with the ones we bought them as a bridesmaid didn't like them, so they were on their own after that.