Having purchased a small tin of the correct colour - Victorian Maroon - from the Locoworks stand at the 2016 National Garden Railway Show, I set about remedying the situation on number 1. Painting the safety valve bonnet was my chosen option as it is smaller than the dome and therefore less painting would be involved! After giving the safety valve bonnet a good degreasing in the dishwasher, I applied a coat of black self etch primer. The next day I applied the first coat of Precision Victorian Maroon, followed by a second coat 24 hours after that.
I gave Loco number 6 - a Roundhouse 'Millie' - similar treatment, as the loco is black, two coats of self etch primer were all that was required in this case.