When was the 'King of the Mountains' jersey changed into the current polka dot design?

Explanation

The climbing competition became part of Tour de France in 1933. The characteristic polka dot jersey, which marks the best climber, was introduced in 1975. The jersey is white with red dots because the sponsor of the competition in the mid 1970s wanted more for its money. It was the company Chocolat Poulain, who used white wrapping with red dots for its chocolate bars. Thus, this also became the colours of the jersey.