In response to screen retention/burn-in issues on the Pixel 2 XL, Google announced last month that it would encourage developers to adopt a light navigation bar. Gmail with version 7.11 is the latest app to switch, while also adding shortcuts for Google Calendar and Contacts.
Like on the Google app earlier this month, the brighter navigation bar fits Gmail given the white background of messages. This light bar is present in all inboxes, messages, and when drafting emails.
However, the previous black bar does return when a keyboard is open or when in settings. This change is currently live on Pixel and Pixel 2 devices running Android 8.1 as part of the current developer preview. In my testing, the dark bar remains on devices running Android 7.1.
Version 7.11 also adds shortcuts for “Google apps” in the navigation drawer. It is at the very bottom of your labels list and just above Settings and Help. At the moment, it has links that will open Calendar and Contacts. It is similar to the shortcuts in Google+, but a bit more useful and fitting the productivity nature of Gmail and those work apps.
This update to Gmail for Android is widely rolling out now via the Play Store.