Maintenance of Way Cars -Painting

[Sunshine Express]

I have made three Roundhouse Maintenance of Way Cars  from a kit,and am asking if all such cars are painted grey?. I am modelling mainly in Old Time Union Pacific and Santa Fe,with a some  Central Pacific .
If I have a choice of any of these roads,   ,then what colours are suggested please ?.  Thanks, Owen

[Sunshine Express]

Thank you Hunt from Owen down under.   Happy New Year to all  on the forum