John Pryke's ballast

I’m hoping (and I’m confident) that someone may be able to help me out with this question.

Does anyone happen to know what kind of ballast John Pryke has used in his yard section of his New Haven, Hartford layout. I would like to duplicate that colour on my layout, but am not sure whether or not this is a mix of a few colours or if it is a ballast that is ‘pre-made’ from a certain manufacturer?

His colours mimic best as to the type and colour of ballast I want to use on my layout.

Thanks in advance,

Chris