Great pictures there.
A medium grey seems to be in the majority, but some look lighter, and some look darker grey like yours.
I was tempted to paint the next three a darker shade like yours, but now think not.
As an aside, these cheap coaches are costing me loads.
I have purchased the following,
1. Bachmann maroon Mk1 brake van as in photos to go with three of these.
2. Bachmann SR green Mk1 restaurant car to make a rake of four.
3. Another Maunsell to make a rake of four.
4. Waiting on three Hawksworth coaches (may get a fourth or use one of these)
A rake of four coaches is just about right for my small layout.