Toward the end of WWII, with resources becoming scarcer by the day, the Luftwaffe did all they could to keep their remaining aircraft looking good. Of huge concern was the propeller, as this would be the first thing that the ever present allied bombers would see when they met them. Top official ordered that all fighters should maintain a pristine & shiny propeller as part of the propaganda war to convince the enemy that the defending Luftwaffe were in a better condition than they actually were.
With many of their bases in ruins & operating from makeshift facilities around Europe, it became ever more difficult for the ground crew to get their fighters into the (now non existent) paint shops for their weekly "prop paint". Some ingenuity was required to address the issue;
Suitably equipped ground crew, with a tin of black, a tin of yellow & two brooms (one marked schwarz the other marked gelb), restrained by a safety harness would approach the aircraft from the front;
Occasionally this would be carried out by civilian subcontractors;
At which point the chief would take over control of the operation, working with the engineer on-board to obtain optimum RPM for paint application;
The painter would then approach the spinning propeller & edge his paint soaked brush forward onto the prop disk, this process allowed the propeller to be rapidly painted, without the need of the paint shop, or even ladders (aluminum was in short supply).
Due to the prestigious post of "prop painting" & it's higher pay rate, sometime ground crew rivalry between the engineers & painters would get out of hand. This picture shows Hermann the engineer seconds before he applied full power in an effort to get rid of Wilhelm (the painter on his crew) & take over his position;
Hermann's efforts were wasted, as Wilhelm dived to the ground, safely avoiding the ensuing catastrophe. Unfortunately for Hermann, the extra RPM he demanded caused a substantial amount of black paint to be drawn through the propeller & sprayed toward him - amids the confusion Hermann didn't throttle back until it was too late;
(Note that the painters gazebo can be seen directly behind the aircraft).
It wasn't until near the end of the war that the Allies came to understand the rapid demise of the Luftwaffe, the air force that thanks to some clever painting had their enemy fooled, when they found a "prop painting rig" after capturing an airfield;
The drum of paint which the aircraft has run over seems to indicate further ground crew rivalry problems, as does the strengthened painters restraining frame.
Note that in the original uncensored picture that the painters gazebo is directly behind the left wing of the P-51.
In answer to the original question, yes it is 100% true that the yellow paint was used to stop the black sliding. Don't be fooled by props that appear to be all black, they still use yellow paint at the tip, but it has been died black for reasons of subterfuge.
Any aircraft industry insider will openly tell you that all propellers are actually painted black, with a yellow "slip stop" coating applied to the tips, they just some times appear to be white, silver or whatever because the black & yellow paints have been dyed for camouflage or cosmetic reasons.
Some smart *** on the A400M project for some reason attempted to "buck the trend" and make it's props in a bizarre black/yellow/black/yellow format. Rather that admitting defeat on this & having a regular prop paint format, they have added an extra 4 blades to each prop, put a kink in the blades & have even got some of the engines running in reverse - but the black keeps sliding off.
Note the painters gazebo at rear!!