Darkmode for Google Playstore was officially rolled out with Android 10

Google Play Store - Xda Developers

Google has at long last begun revealing the dark mode update for its Play Store, after the arrival of Android 10. With the new update, all applications on the Play Store are set to step by step get their very own in dark mode theme. A dark themed Play Store is being rolled out on Pixel handsets at now. The new dark theme design is by all accounts accessible for a limited number of users until this point, yet would rolled out globally very soon.

Also, the Gmail application has just begun getting the dark mode update and is said to be accessible with  2019.08.18.267044774 version, which is as of now accessible on Play Store. With Android 10's operating system the dark mode on its own applications(Google), however other third party applications that have the access to go for dark theme.

Google has issued the Android 10 OTA update for all Pixel cell phones. One can check for new software updates by means of Settings > System > System updates.