The change is very minor - the button has gone from a fairly ordinary, muted forest green to a much brighter, minty neon shade.
It's such a small change that some users have started asking whether their eyes could be playing tricks on them.
To be fair to Twitter, it's not as drastic as the November change from star-shaped 'favourites' to heart-shaped 'likes', but it's still managing to unsettle a few users.
Twitter seems to be conducting a few design tests on small groups of tweeters at the moment - many have taken to the social network to complain that their like and retweet buttons appear to have moved from their usual positions, to be more in line with the text of the message.
who at twitter decided the new retweet button green was a good green— ⁂ (@PolClarissou) February 3, 2016
its a Bad green
take that green away
did twitter change the shade of green for the retweet button or have i gone mad— ｔｉａｈ (@sleepywave) February 3, 2016
Wait, has Twitter just changed the shade of green in the retweet button in the last minute?— Jeremy Duns (@jeremyduns) February 2, 2016
It's not clear whether the new button is just a test or a permanent change, and there's currently no indication why the colour was altered in the first place.
We've reached out to Twitter for a comment to get to the bottom of the mystery, this article will be updated when they respond.