And fans were left asking why Real Madrid would do such a thing after initially wearing purple throughout the course of the game.
Regardless of the colour, Zinedine Zidane's side were a class above as they put Juventus to the sword and became the first team to retain the trophy in its modern format.
Cristiano Ronaldo was the hero, scoring a brace in Cardiff 13 years after scoring for Manchester United on the same ground as a teenager.
Casemiro and Marco Asensio also struck to give Los Blancos their 12th tournament triumph.
And Real players celebrated in their home kit down to a rule imposed by governing body UEFA.
Real Madrid's Champions League player ratings against Juventus Sat, June 3, 2017
Express Sport brings you Real Madrid's player ratings from the Champions League final against Juventus
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Keylor Navas – 7.0
Real Madrid beat Juventus to win the Champions League
Real Madrid changed into their home kit because of a rule imposed by UEFA
The rule means that players must celebrate in their normal jerseys – which explains why John Terry stripped down to wear Chelsea's blue shirt after winning the competition five years ago.
Manchester United, however, went against protocol by remaining in their away kit after beating Ajax to win the European League last month.
Ronaldo, who led the celebrations, insisted he deserved to win the trophy after scoring 16 goals in his final 10 games of the campaign.
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"I prepared myself for this, you win the biggest prizes because of what you do at the end of the season," he said.
Cristiano Ronaldo scored to inspire Real Madrid to Champions League glory
"Zidane gave us a very positive half-time team talk and told us he really believed in us.
"It has been an incredible end to the season by us.
"We are the first team to win it two years in a row and I scored two goals.
"It's another record for us and the players deserve it and so do I because I scored twice and I'm the top scorer in the Champions League."