A video posted online shows a man in a three-piece suit using a fire extinguisher to spray the glass exterior of the building in King’s Cross, London, with the bright paint.
The footage was shared on the Facebook page of the Burning Pink Party – the party of London mayoral candidate Valerie Brown.
In a post, the party claimed the man was “holding The Guardian to account for breaking their climate pledge”.
It later went on to say the stunt also aimed to hold the newspaper to account “over their utter failure to report on London mayoral candidate Valerie Brown”.
In the bizarre footage, the protester, wearing a bright pink tie and eye mask, can be seen eating a raw carrot as he stands back to admire his handiwork.
Photos published by the Camden New Journal show staff with power hoses attempting to clean up the aftermath on Friday.
The Metropolitan Police said a man in his 50s had been arrested on suspicion of criminal damage in relation to the incident.
The force said in a statement: “Police received a report of criminal damage at an address in York Way, N1, at 10.02am on Friday 7 May.
“Officers attended. A man aged in his 50s was arrested on suspicion of criminal damage and taken into custody.
“A number of other people are believed to have left prior to police arrival.
The incident came just a day after protesters targeted HS2’s London headquarters, which is shared with Network Rail, in a similar stunt.
Two men scaled the building in Euston before using fire extinguishers to cover it in pink paint.
The activists were members of the group HS2 Rebellion, which opposes the construction of a new £65bn high-speed railway linking London to Birmingham, Manchester and Leeds.
The group, which fears the network will increase carbon emissions, said the protesters were raising awareness of the need for a citizens’ assembly on London’s infrastructure.