European Professional Club Rugby is to apologise to Cardiff Blues and Glasgow Warriors over Sunday's kit clash.
The sides met in a Champions Cup clash at Cardiff Arms Park with both wearing blue kits - Glasgow's attire being marginally lighter.
Cardiff's Wales international Gareth Anscombe was scathing about the situation and said: "I don't know who the guy's job is to decide that, but he has got to face consequences for it.
"It was an out and out disgrace.
"I have never come across that in my eight years of playing rugby. Who is making those decisions?"
The tournament organisers said in a statement on Monday: "EPCR has procedures in place for ensuring that playing kits for matches in its tournaments are distinctive.
"However, these procedures were not sufficiently followed through for last weekend's Heineken Champions Cup, Round 2 match at Cardiff Arms Park.
"EPCR will be formally contacting both Cardiff Blues and Glasgow Warriors in due course to apologise."
Glasgow won the match 29-12 to open their Champions Cup account for the season.