If you check my previous post here:
TMP link
you will see odd references to hand guns in Lancastrian hands.
See 1449: Lord Moleyns (as Lord Hungerford) was a Lancastrian and Lady Paston said he had guns.
See 1460: John Dynham was a Yorkist and was clearly shot by a Lancastrian handgun.
What we can conclude from this is that handguns had been known in England since at least 1385 (Bodiam Castle, Cooling Castle and the West Gate at Canterbury all have 'upside down keyhole' gunloops) but handguns do not appear in large numbers until the mid-15th century.
A small unit or sub-unit of hand gunners in a major Lancastrian lord's retinue, such as the Duke of Somerset, would be OK. In which case the jacket colours would be white/blue when viewed from the front.
See:
link
The nearest man is one of Somerset's retinue.
If French handgunners then this is ideal:
link
French hand gunners at Bosworth – a white cross of St.Denis worn over red but other colours are possible.
Barry Slemmings
author of Bills, Bows and Bloodshed 2.2