I went through the blue one (I believe it's the 2nd edition).
However there was a girl in my PBL who went through the red one (3rd edition).
Every week (i.e. for each topic/organ system throughout the year) she'd make a short "quiz" for our group with 10 questions, and every time, all ten were covered from my own copy of the book.
Therefore, my guess would be that they are generally the same.
I can also comment that I own both Kaplan QBook 3rd edition and 5th edition, and all of the questions are the same (I got one of the books for free).
It's a malfeasance that these guys can sell the same product as a newer edition and people still buy it. I think they just change some of the errors or explanations, but the material is essentially the same.
heck, can I even just use the 1st edition of the robbins q/a book (to be honest, theres online editions floating around of the 1st but no other editions)
Depends on what u are using it for. I used 3rd edition and it had the matching page numbers for most recent papa and baby robbins. 1st edition wouldn't. I'm sure u can buy it for like $5 on dealoz.com why bother using a pdf.