Altogether this is a photo I really like. For the blonde the dress has a nice use of light source however I felt that if you were to add some darker shades to the dress & the entire "model" it would make the really light colors pop. Also it was a bit hard to read the platinum blonde "sign."
For the ginger red I believe you have a really nice design for her dress. I also like her posture. It made her look classy & strong.
For the chestnut brown, first of I love her pose. Her outfit has a very bohemian feel & I like it. The shoes added a cute detail to it.
For the raven black she has a very sinister yet elegant look. I totally love it. Her pose makes her look very royal.
Last but not least Alternative pink. I don't have alot to say about it but I really do love how her dress goes from dark to light.
That platinum blond coloring is a bit difficult to read against that plain white backround, but the design still looks good.
My personal favorite is the Ginger Red since I am fond of vibrant colors and redheads. Second place favorite would have to be Raven Black, the name and nature of the hair color is displayed well in the design of the dress and the attitude given the model.
My least favorite is Alternative Pink; the lower half of her dress feels similar to the lower half of Raven Black's dress, only slightly, but enough to stick in my mind.
I looked over this several times and didn't see the "Platinum Blonde" label until I read the critiques and knew it was there. (I thought before that revelation that for some reason you had decided to omit a title for that dress and was fairly confused.) So yeah, it's VERY hard to see and would not have noticed it if its existence hadn't been pointed out by the other comments.
Other than that, I like the dresses. Brown's interests me the most for some reason - I guess because the posing and the design just seem so adventurous? I can't picture myself wearing a dress quite that risque but the "model" of your choice pulls it off well and it looks just bold enough to stand out amidst the other more conservative looks. Raven Black and Platinum Blonde remind me of the villainess and princess in the cartoon version of "Swan Lake" respectively, the villainess in particular. Lovely but...a little too anime-standard to stand out I guess?
Very nice job overall though. And belated congratulations on the DD. :]