【99 Moons】

Did you9 Moonsa little trouble distinguishing between teams at the World Cup opener? You weren't alone.

During the opening game between Saudi Arabia and host country Russia on Thursday, people watching who have colour blindness complained on Twitter they had trouble identifying which team they were cheering for.

Why? The teams wore red (Russia) and green (Saudi Arabia), two of the colours people with a type of colour vision deficiency (CVD) are unable to distinguish between.

More than a few people were upset.

This Tweet is currently unavailable. It might be loading or has been removed.

This Tweet is currently unavailable. It might be loading or has been removed.

This Tweet is currently unavailable. It might be loading or has been removed.

This Tweet is currently unavailable. It might be loading or has been removed.

This Tweet is currently unavailable. It might be loading or has been removed.

Some picked out any possible way to distinguish between the two teams, however small.

This Tweet is currently unavailable. It might be loading or has been removed.

It's not exactly a niche problem, with CVD affecting approximately one in 12 men (8 percent) and one in 200 women in the world. It's more common in men as it’s carried on the X-chromosome.

Improving the experience of people watching football with CVD isn't a new idea — even coaches and players within the industry deal with it, including Norwegian coach Lars Lagerbäck.

The English Football Association and UEFA teamed up with the UK's Colour Blind Awareness organisation last year to produce a guide booklet as part of a campaign to maximise awareness. Suggestions include avoiding kit clashes, and rethinking use of full red and green uniforms on a green pitch (like the World Cup opener).

"Colour blindness is an important issue in sport — for players, spectators, and investors — from the grass roots through to the highest professional level," reads a statement on the Colour Blind Awareness website.

"It can impact on a person’s performance, spoil the enjoyment of watching sport (live or on TV) and have an adverse effect on revenues if colour blind people turn their back on sport in frustration."

Could be something to consider for the rest of the World Cup?