“I used to be a lifeguard until some blue kid got me fired”

A racial joke about employment has been told by stand-up comedian Larry the Cable Guy since at least 2005:
 
“I used to be a lifeguard until some blue kid got me fired.”
 
The joke is that the “blue kid” is someone who was gasping for breath, and the lifeguard didn’t help him.
   
         
Wikipedia: Larry the Cable Guy
Daniel Lawrence Whitney (born February 17, 1963), known professionally by his stage name Larry the Cable Guy, is an American stand-up comedian, actor, producer, singer and radio personality, with a career spanning over 30 years.
 
8 February 2005, Reno (NV) Gazette-Journal, “Cable Guy wires his audience” by Brandy Dela Vega, pg. 3:
As soon as Larry saw his bare-arm image plastered on the center’s four overhead stadium screens, he assured the audience he used to be in better shape.
 
“I used to be a lifeguard,” he said. “Until some blue kid got me fired.”
     
22 April 2005, Milwaukee (WI) Journal Sentinel, “Review: Larry the Cable Guy’s bare wit starts to wear thin” by Dave Tianen, pg. 8:
“I used to be in good shape. I used to be a lifeguard until some blue kid got me fired.”
       
Slate
Larry the Cable Guy
America’s favorite redneck.
By BRYAN CURTIS
NOV 02, 20056:23 PM
(...)
Dressing for all of them, Larry mounts the stage in a sleeveless flannel shirt, jeans, and a ball cap adorned with a fishhook. “I used to be a lifeguard,” he says, “until some blue kid got me fired.”
 
Google Books
The Snark Handbook:
A Reference Guide to Verbal Sparring
By Lawrence Dorfman
New York, NY: SKyhorse Publishing
2009
Pg. 45:
I used to be a lifeguard, but some blue kid got me fired.
     
Yahoo! Answers (May 7, 2009)
what’s with the saying “I used to be a lifeguard, but some blue kid got me fired. ” ?
l keep hearing this as a funny one liner.. but l don’t understand the significance!! Help!!
Best Answer
nerdcore
Blue = skin color of someone who drowned.  So a drowned kid got the lifeguard fired.  Get it?
 
Reddit—Dadjokes
Posted by u/HoshForce March 4, 2019
I use to be a lifeguard, until some blue kid got me fired.
   
Reddit— Oneliners
Posted by u/rinkgirl August 15, 2019
I used to be a lifeguard until some blue kid got me fired.
 
Reddit—3amjokes
Posted by u/joyfuldig November 30, 2019
I used to be a lifeguard until some blue kid got me fired.