This first one - I think - comes from the early 1980s. It is a north-bound morning service.
Around the same time the repainted versions were appearing. This 4 car set carries the white ' reverse 7' logos, which made them go faster and not break down.
Once done with the reverse 7s, some sets got the 'reverse' paints job. These ones went even faster.
Finally, the painters went for the fastest colours in their tins - red and orange.
Sadly this did not further improve their speed or longevity.