Customizable accent colour on Tusky

[OrchidLuna]

Pitch

The accent colour on Tusky is blue by default. Since I don't really like blue, allow users to customize Tusky's accent colour. Defaults to Android's default accent colour or the colour set on Android Settings, and having variety of accent colours users can choose.

Motivation

A favourite colour represents the person's personality. Having customizable accent colour on Tusky makes the app more comfortable to use.