I still think his sidecap and tie are coloured in, certainly the tie should be khaki, the sidecap has a "tail" that nearly touches his eye, (a mistake by the colourer/)
I did consider Surrey Yeomanry who were an integral part of the 98th Regiment R.A. at B.E.F. and Dunkirk, the badge is indistinct but with some shape of the top half of the Surrey Yeomanry.
James