The latest stable official firmware remains based on Android 6.0 (ColorOS 3.0).
In mid-2018, Oppo’s India support team publicly stated: oppo f3 android 8 update download
While there were earlier reports and rumors regarding a Nougat (Android 7.0) update, Oreo was generally not considered part of the official update path for this specific MediaTek-based device. The latest stable official firmware remains based on