I wouldn't use a comma after 'young' because I regard 'college-educated adult' as one unit. At least I have no reason not to view the phrase this way. In some textual contexts 'college-educated young adults' might be the required arrangement, but in that case I'd see 'young adults' as one unit.
Here's another example: we're talking about 'hand-made shoes' which cost a lot of money. 'Lobbs are the best-known makers of hand-made, very expensive shoes.' To me, that sounds strange because we aren't talking about 'very expensive shoes'. It should be 'very expensive hand-made shoes.' There's only one adjective, 'very expensive', so there's no need for a comma.
There are sometimes differences between American and British punctuation, or even between individuals. Use of hyphens is a good example, by the way.
I was taught to always put a comma between adjectives. Later I found that the "rule" was not followed religiously by many writers, but I always feel "safe" using the commas. The final adjective is separated by "and".
Packard is handsome, brave, intelligent and witty; characteristics that we should all aspire to. (A perfect sample sentence in my opinion.)