In your previous example, you are referring to the inherent quality of each color. They are, or may be, bright/bold/understated/unpleasant/different from each other/appealing to a certain market etc. Someone could say...these are different colors ....it would be perfectly reasonable to respond .....they all look pretty bright to me. That's because they are relatively subjective differences.
In the example on this page, we are talking about different in a literal/objective manner. Someone is holding up two dresses or they are being told to wear different dresses than the ones they planned. The different dresses or their concept exist separately from each other in a manifestly real way. If you hold up two dresses and say ....different dresses...... no one will respond ....but I see only one dress. That's because they are literally objectively different dresses.
We know that Duo means the latter take on different dresses in this example because they placed different after the noun.
Subjective/figurative adjectives go in front of the noun. Objective/literal adjectives go after. Sitesurf says about ten per cent can go either way depending on intended meaning. Where you place them depends on what you are trying to say.
Kudos to Duo for this example. Well timed and well constructed to generate thoughtful consideration by some students.
The "some" is the closest translation of the partitive article du/de la/de l'/des. It is not an exact translation though, and in many cases is the English translation better without the "some". English do not need anything that fills the function of the French partitive article.
Any has another function in the sentence than the partitive article. "Different dresses?" and "Any different dresses?" do not have the same meaning. The first question is more a question of surprise or need of explanation whereas the second is a question of the existence of other dresses or of interest in other dresses.