Since the MATE Desktop migration to GTK+3 some some buttons started to look like this:
Soon in Ubuntu MATE 17.10 they will start to look like this:
You can thank @lah7 for presenting an impassioned argument to return the button to a more traditional style when we met at the Snap sprint in London earlier this year 
Tradition by default, freedom by option? Seems like a good option for “Mate Tweak” 
This is a theme change, not something you can toggle in MATE Tweak. Also, only message dialog button are affected. Linked buttons do make sense in other places and they continue to function normally there 
For the visually impaired amongst your users, this is a huge improvement. Being able to see where one button starts and another ends makes a difference! Thank you for listening. It’s something UM does really well.
Ubuntu Mate has proven itself, over time, via the thoughtful choices of its devs, to hold to a design principle of being traditional and thoroughly modern simultaneously.
That’s not always an easy balancing act to maintain - especially when one is dependant on developments occurring outside of one’s control. But, the Ubuntu Mate team has delivered on it time and again.
Thank you Martin and the rest of the UM team.
Speaking of that, Discord made the regrettable decision to conjoin the video and voice chat buttons for the video mode beta, with only the pointer illuminating where the cursor is. I can see an argument about how somebody would select one or the other by accident due to this.
I agree with the change, The traditional look is why I changed to and why I am in love of Mate Desktop.
The way people are familiar with the desktop, no wheel reinvention needed.
I know I’m biased… but dang… those buttons (did) look horrible! 
A big thanks, Luke @lah7!
@Wimpy
Speaking of tradition, any chance of bringing back the Customize Theme/Colors we lost with the transition to GTK3?
It makes a considerable difference to me.
ditto, though i’m not using 17.10 yet because i can’t download the freakin’ iso file here in the boonies.
2 posts were split to a new topic: What happens with regard to third party apps during an LTS -> LTS upgrade?
Go Luke! I think it looks better the old way myself
Yes. It takes work to make it look good. They put thin lines like that between everything and you can’t hardly see where the buttons begin or end.
Looks like a positive move to me. I had thought that the overlap of the button edges might be a bug, a problem with my graphics driver or some other rendering issue!
Ouuh thank you @lah7 so much!
There are so much other (useful) challenges in a live than to search for nearly invisible button boundaries… 
I like easily understandable generic buttons. It’s what I think a golden category old style thing. Inspirational because old and simple puts focus on life and work. I don’t mean the Apple fashion fancy simple of course. My opinion on style changes is why not make the old version available as well every time? Choice always adds extra value to products.
I’ve just checked this in UM 17.10 and the buttons are still showing the older design for themes such as OSX Arc, I’m assuming this is only specific to certain themes that have this change implemented?
