SYWEB-194: Tweak unread message background colour
SYWEB-194: Tweak unread message background colour

So it displays better on different kinds of monitors.
williamboman/matrix-angular-sdk,williamboman/matrix-angular-sdk,matrix-org/matrix-angular-sdk,williamboman/matrix-angular-sdk,matrix-org/matrix-angular-sdk,matrix-org/matrix-angular-sdk