A riddle about M&Ms is:
 
Q: Why do blondes hate M&Ms?
A: They’re too hard to peel.
 
The joke was posted on the newsgroup rec.humor on May 7, 1992.
 
       
Wikipedia: M&M’s
M&M’s are “colorful button-shaped chocolates”, each of which has the letter “m” printed in lower case on one side, surrounds a filling which varies depending upon the variety of M&M’s. The original candy had a milk chocolate filling which, upon introducing other variations, was branded as the “plain” variety. “Peanut” M&M’s, which feature a peanut coated in milk chocolate, and finally a candy shell, were the first variation to be introduced, and they remain a regular variety. Numerous other variations have been introduced, some of which are regular widespread varieties (such as “peanut butter”, “almond”, “pretzel”, “crispy”, “dark chocolate”, and “caramel”) while others are limited in duration or geographic availability.
 
M&M’s originated in the United States in 1941, and are now sold in as many as 100 countries.
     
Google Groups: rec.humor
BLONDE JOKE LIST
Belding, Troy C.
5/7/92
(...)         
Q:  Why do blondes hate M&Ms?
A:  They’re too hard to peel.
 
Google Groups: alt.sex.stories
blonde.txt 3/7
The Road Warrior
2/15/94
(...)
Q:  Why do blondes hate M&Ms?
A:  They’re too hard to peel.
   
Google Groups: alt.support.post-polio
BLONDES/BIMBOES
Marilynn R. Bierman
3/1/96
(...)
Q:  Why do blondes hate M&Ms?
A:  They’re too hard to peel.
 
Google Books
Unbelievably Gross Jokes, Volume 27
By Julius Alvin
New York, NY: Kensington Pub. Corp.
1998
Pg. 88:
Why do blondes hate M&Ms?
They’re too hard to peel.
   
Google Groups: alt.humor
Blondes
.(JavaScript must be enabled to view this email address)
2/27/98
(...)
Why do blondes hate M&Ms?
They’re too hard to peel.
   
23 October 1999, Central Coast Herald (Newcastle, New South Wales), “Weekend,” pg. 2:
Why do blondes hate M&Ms?
They’re too hard to peel.
 
Twitter
Firux‏
@iheartspooning
Replying to @JonasAlerts
@Karen_Sanchez Why do blondes hate M&Ms? .......  They’re too hard to peel 😊
6:15 AM - 31 May 2009
 
Google Books
The Ultimate Book of Blonde, Brunette, and Redhead Jokes
By James Buffington
Berkeley, CA: Ulysses Press
2010
Pg. 53:
Why do blondes hate M&Ms?
They’re too hard to peel.
   
Google Books
Sensible Nonsense.. Frank’s Comic Pack:
Humour Pack Series
By Frank Paul
BookBaby
2014
Pg. ?:
Q: Why do blondes hate M&Ms? A: They’re too hard to peel.
 
Twitter
GET LOLIFIED!‏
@TheLOLWorld
JOKE: Why do blondes hate M&Ms?
They’re too hard to peel. http://ift.tt/22Vj3cg
5:04 PM - 7 Sep 2017