Yahoo Mail's beta version app has received quite a little update recently as the Yahoo development team brings material design visual improvements to the UI. Currently the changes can only be seen in the beta version so for those who are still using the normal app that can be downloaded from the Play Store, everything looks as it did before the visual refresh came to the beta. When users get their hands on this version of the app or when Yahoo decides things are finally ready for primetime and pushes the changes to the main app, the first thing users will likely notice is the complete visual overhaul with material design.
Looking at how the UI design is set up now, it's quite possible that Yahoo still has some finishing touches to put on the app before it sends things out to users. The header bar up top is deep and full of color just like other material apps, and the hamburger menu now evokes more of a material design style, one part seems a little out of place though; the floating action button. While the presence of the floating action button itself is nice to see finally making its way to the official Yahoo mail app, one need only look at the screenshots below to realize that it seems to be a tiny bit out of shape. The floating action button should be round but as shown in the images it doesn't appear that way. Having said that this does appear to be something Yahoo implemented intentionally as the FAB matches the shapes of the contact icons in the mail list.
Another stark change is the bold use of the gradient style color scheme throughout the application. Most other material design apps would be opting for 2 or 3 solid colors layered throughout the UI, perhaps with the header and the FAB matching each other or with the FAB matching accent colors in the hamburger menu. Instead, Yahoo has gone with a full use of gradient including dark and light purple hues across the entire application from the main screen to the settings menu. The overall design of the app looks nice, and users will surely get accustomed to it if no changes are made, but things might look a little more in line with the material design guidelines if Yahoo changed up the FAB to match the solid dark purple color they're known for. It's also worth mentioning that this is Yahoo's beta version so they have some time to play with things, and you have to give them credit for striking out and trying something different.