Its probably worth checking out the February issue for Diesel content, Sound in a Dapol 08 in 7mm and a small contemporary station and wagon works in 4mm.
The advert for April includes images of a DMU(N) and a Class 24 (00 - and on my mainly Blue Dock Street so I will declare an interest) plus a very old steam engine...
The relatively recent 4mm project layout by Chris Ford was blue diesel.