lilyyang,
It is hard to know exactly what the authors of that manual were trying to get across when they wrote the dialogue about “that great little red dress,” or whether they even gave much thought to ‘little’ or ‘great little.’
As some have surmised, it could be that the dress is short in length. Or it could be that she wears small or petite (extra-small) sizes, so the dress is small in size. She definitely thinks the dress is great (wonderful, fantastic).
However, it should be noted that although the English language does have diminutive forms (booklet, miniskirt, doggy, etc.), as well as numerous diminutives borrowed from other languages, the English language does not have what is known as a ‘productive’ diminutive form; that is, one that can be used with nearly any noun. Whereas in other languages, a ‘productive’ diminutive form is quite common.
For example, in Dutch the -je ending (or a variation thereof) can be added to just about any noun. A fantastic ‘little’ restaurant is ‘een fantastisch restaurantje.’ A nice ‘little’ drive (in a car, or ride on a bike, train ride, etc.) is ‘een gezellig ritje.’ A nice ‘little’ meal is ‘een lekker etentje.’
Oftentimes English speakers use the word ‘little’ in the same way: as a diminutive ‘term of endearment.’ It doesn’t necessarily have anything to do with size or length (although it certainly can). ‘Little’ can just be a modifier to show that something is ‘endearing.’ (It should also be noted that it can also be used sarcastically to show that something is not so endearing.) It is most commonly used with another modifier: nice little, cute little, perfect little, tiny little, great little.
Example: (no sarcasm)
When we were in Vermont, my wife and I went for a fun little drive in the countryside. We stopped off and had a nice little meal at a great little restaurant. Then we came upon this wonderful little furniture store and there was this awesome little couch that I wanted so badly, but we couldn’t really afford to have it shipped. So we left there and then we found this fantastic little clothing outlet and while my wife was trying on a cute little outfit, I snuck over and bought one of those beautiful little decorative eggs that she loves so much.
Someone on Twitter wrote about a “great little red ale,” while someone else wrote about a “great little red wine.” In the attached photos, there is nothing little (small) about the size of the bottle of beer or wine. It could be that the red ale was made by a microbrewery or that the red wine was made by a small winemaker, but more than likely it’s just a diminutive ‘term of endearment’ for the wine or the beer, without any thought as to the size of the manufacturer. They definitely think it tastes great.
Other examples from Twitter:
A “great little red number” (the word ‘number’ here actually refers to an article of clothing, namely a dress). The model wearing the dress is tall and slim; the dress is neither particularly short nor small.
A “great little red hat.” Nothing especially small about the hat.
I think you get the idea.