If you've been to a bridal shop then you'll have probably noticed that they only tend to have one of each teal formal dress in stock, normally in just one size and in one color. There are a few reasons why, the two main reasons is cost and space. Each store has to buy a minimum number of teal formal dresses from their designers once or twice a year, and they have to pay for them. So it's incredibly expensive to have a large stock of dresses all the same in different sizes or colors. There's also the space issue, if each style comes in just 10 colors and 8 sizes, then that's 80 dresses per style to fit into the boutique, and if that dress is discontinued the following year it's an awful lot of dresses to sell off the following season, that's hoping 20 brides come in wanting that one style each with 4 bridesmaids all in different sizes.
Bridal shops require brides to use their imagination or the online color changing tools from the designer for choosing the style and the color for their dresses.
In short, having one of each dress allows brides more choice when choosing their teal formal dresses, it just takes a little imagination and faith.