You may have read the wildly popular BBC blog post about ‘great green dragons’ recently.
Now take another look at the title of this post — did you notice the comma between the second pair of adjectives? Why is English so confusing?
The official terms for using commas in these two instances are cumulative and coordinate adjectives.
‘Great’ and ‘green’ are cumulative adjectives (they build on each other to describe the dragons). They don’t need commas. You may know this by instinct, or you can test it by putting ‘and’ between the adjectives and trying them in reverse order.
So ‘green great dragons’ doesn’t sound right, and neither does ‘green and great dragons’. No comma needed. (Similar examples are ‘a happy little boy’ or ‘a rusty old car’.)
‘Soulful, shiny’ are coordinate adjectives (they’re on an equal footing in the description). Use the same test: you can say ‘shiny, soulful eyes’ and you can also say ‘soulful and shiny eyes’. So you need a comma between them. (Similar examples are ‘a gentle, kindly soul’ or ‘the long, winding road’ — to paraphrase the Beatles.)