Android 8.1 removes the sRGB toggle from the dev settings, meaning that if you were fond of this feature that can be found in the developer options portion of the settings menu, you won't have this available once you either install the dev preview or install the final public release once it gets pushed out by Google in the future. If you're on Android 8.0 Oreo, navigating to the settings and then to developer options if you have enabled would show the Picture Color Mode setting with the toggle right next to it that would turn on the sRGB colors for your display.
Why Google chose to remove this from the software with Android 8.1 in the developer preview isn't clear at this point, but it's worth mentioning that this is a dev preview so Google could always add it back in the final release. That said it's also possible that Google has chosen to remove it for good and it won't be added back in even when the final version is sent out to users later on. This will leave users with a little bit less control when it comes to calibrating the colors of the display moving forward, but there are likely apps which could be installed that would open up these features in the event that Google doesn't make it available again as a native option.
One other thing to consider is that since this is hidden away in the developer options menu, which many users will never access, Google could have seen fit to remove it due to it not getting much use, or perhaps it has plans to add something else back in which makes it automatic, or perhaps it will move the toggle to a different part of the settings or incorporate into a different function, possibly in the display settings. Whatever the case, the feature is now gone, so if you're on the dev preview for Android 8.1 already and you did use this mode before, you'll need to find an alternative if possible. In addition to this change, the dev preview has also revealed a handful of other changes, like the change from the "apps running in background" alert to the "apps consuming battery" alert, and the notification shade changing colors to match colors in the background.