Function step_text_color_transitions 

pub fn step_text_color_transitions(
    commands: Commands<'_, '_>,
    tick: Res<'_, Tick>,
    anim: Res<'_, AnimationsActive>,
    q: Query<'_, '_, (Entity, &TextColorTransition, &mut TextStyle, Option<&Visible>)>,
)

Sample every active TextColorTransition into TextStyle::color.