When Wales and Portugal stepped out for their Euro 2016 semi-final both wearing their away kits, fans were very confused.

Sure, both teams normally wear red so somebody had to use their change strip – but was there any need for both of them to do it?

Well, hold your irritation, football fans – it turns out there was a very good reason.

While the change of kits might have been annoying for traditionalists, it was great for anyone with red-green colour blindness.

The picture on the right shows how the match looked to some colour-blind people – and you can see the two kits are very distinct from each other.

This hasn’t always been the case throughout the tournament – look what happened when Portugal took on Croatia in the last 16.

With one in 12 men (and one in 200 women) affected by colour blindness, a colour clash like that can leave thousands or even millions of viewers unable to distinguish between the teams.

Kathryn Albany-Ward, founder of Colour Blind Awareness, said: “Uefa has taken an interest in colour blindness and we’re in regular contact with them. They appreciate our advice and guidance regarding the colour blindness issues arising in football.

“We’re delighted with the kit choice for the two teams at the Lyon semi-final, because had Portugal played in their red home kit against Wales in their ‘charcoal’ away kit this would have meant that 25% of the colour blind viewers wouldn’t have been able to tell the teams apart.

“This is because they have a type of red/green colour blindness where dark reds appear black.”

So the change of kit last night may have looked odd – but there was a very good reason for it.