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.
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.
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