They turned out to be part of a promotional campaign by a charity encouraging players to help tackle anti-gay abuse in football by replacing their regular boot laces with the gay rights symbols for this weekend's games.
However, the initiative has managed to antagonize leading clubs and led to the football authorities expressing reservations about the publicity-seeking strategy employed by sponsors of the campaign. Bookmaker Paddy Power has its branding plastered over the promotional material connected to the initiative — including newspaper ads this week that feature slogans with sexual innuendo— which has caused many football officials to feel uncomfortable about a move that was ostensibly meant to help eradicate discrimination.
European football's top anti-discrimination adviser, Piara Powar, said it seems "product placement has been latched onto a social cause."
Most clubs said they aren't endorsing the campaign, but that players are free to wear the laces if they want to.
Fronting the campaign has been Joey Barton, who plays for second-tier club Queens Park Rangers. While on loan at French club Marseille last season, the midfielder was admonished for describing Paris Saint-Germain defender Thiago Silva as an "overweight ladyboy" on Twitter.
"The campaign is making some people very uncomfortable," Powar, the head of European fans' network FARE, told The Associated Press. "It has sexual innuendo, is clumsy and some people in the gay community are very offended."
The Premier League has backed the rainbow laces campaign's underlying pro-equality message, while questioning the decision of the gay rights charity Stonewall to work with a betting company renowned for its stunts.
"We were not consulted about this particular campaign," the league said in a statement. "Had we been involved earlier in the process we could have worked with Stonewall to consider things like boot deals, the use of particular betting partners."
Another campaign group, Football v Homophobia, turned down an offer from Paddy Power to be involved in the boot-lace initiative because of what it described as inappropriate slogans.
"We feel it is incongruous to run a campaign aiming to change football culture whilst using language which reinforces the very stereotypes and caricatures that, in the long term, ensure that homophobia persists," Football v Homophobia said in a statement.
Likewise, Chelsea communications chief Steve Atkins said the club was uneasy about the "tone of messaging, the lack of consultation and the seemingly commercial part of it."
The only Premier League club to completely endorse the campaign is Everton, which counts Paddy Power among its sponsors.
For Norwich, using Paddy Power's promotional material would have conflicted with the club's own sponsorship with the betting firm SBOBET.
The only openly gay man to play for a British club began his career at Norwich. Justin Fashanu came out in 1990, but was found hanged in a London garage in 1998 at age 37.
"We will not be asking our players to wear the Rainbow laces this Saturday but we are committed to combatting homophobia," Norwich said in a statement, reflecting the views of most clubs.
Stonewall defended its decision to team up with Paddy Power due to the charity's limited resources.
"I can't remember so many people having such a public debate about homophobia in sport," Stonewall spokesman Richard Lane said. "Being able to get that public conversation going has been really invaluable."
Paddy Power, which is renowned for its brash marketing campaigns and was involved in former basketball star Dennis Rodman's latest visit to North Korea, also dismissed criticism over its role and the communications tactics.
"The powers that be seem concerned a week is not enough notice," the bookmaker said. "How long does it take to change a pair of boot laces?"
Rob Harris can be followed at www.twitter.com/RobHarris