If you have more than one Google account, you know that it is usually a snap to change between your accounts. And thanks to a new update Google has turned the UI of the Play Store account switcher to Material Design which includes Dark Mode. The latter inverts the usual dark text on a white background to white text on a white background. This prevents users from straining their eyes and the eyes of innocent bystanders in a dark room or at night.
To swap Google accounts while using the Google Play Store, open the app and tap on your avatar at the right of the search bar; you'll see all of the Google accounts that are signed into your phone. Simply choose the one that you want to use. Note that the account switcher menu on other apps like Google Maps and Google Home allow users to access the app's settings; perhaps this is something that Google can address with the next update to the Play Store.
According to 9to5Google, the Google Play Material Theme account switcher was first tested late last year by Google in one of their infamous A/B tests and has appeared in versions 19.3 and 19.4 of Google's Android app storefront. You can also enable the UI change if you have version 19.3 or 19.4 of the app. Simply go to the Google Play Store's App Info page by tapping Settings > Apps & notifications > App info > Google Play Store. Tap on "Storage & cache," and "Clear storage." Open the app and then close it again from the Recents/Multitasking menu. Follow all this and the new Google Play Material Theme account switcher will be found on your Android phone.