If you come across a multicoloured bridge it’s more likely be ladened with different coloured padlocks than have something to do with a Pride celebration. I’m not sure how popular this trend is across the world, in Canada it’s popular in Ottawa and Vancouver, and in the UK, Liverpool I believe, but it’s on just about every bridge in Europe.
How this works is you buy a padlock, scratch or have engraved the names of yourself and your (current) sweetheart and you lock it onto a bridge, therefore declaring your true love forever. And in true capitalistic fashion there are online businesses selling these locks, offering custom engraving etc., and claiming it to be an ancient custom. I’m unaware of the history of padlocks but I have doubts it is as old as they imply. Also, they are not inexpensive from these businesses that is, you can pick up a cheap one from anywhere and do it yourself. While I can’t say for sure this happens everywhere, I do know that in Prague they are removed by the city council when there are too many, so mind where you place one because you maybe in for a brief romance.
Then of course there’s the do-it-yourself padlock removal ceremony, I witnessed one happen on the Eiserner Steg Bridge in Frankfurt. Oh well, you can always buy a new one.