Actually it's not an Anglosaxon crimson, it's a deep red/light crimson called carmesi in Spanish, Karminrot in German – it doesn't have the wine colour aspect of crimson, it's lighter. Hence your seeing a "red" flag. Spanish uniforms at this time used two reds: carmesi and encarnado – the latter a bright red like fresh meat.
Also, the light cavalry, including dragoons (which Almansa officially were although they dressed as cazadores) carried guidons with two tails, like British cavalry guidons, as opposed to the square flags of the heavy cavalry (described by Keith Over – though only half of them had "crimson" flags anyway, others were blue or white).
So: a deep red guidon.
The Almansa guidon was as follows:
- front: the usual royal coat of arms (flanked by canons, flags etc – the standard design)
- reverse: centre: the monument commemorating the battle of Almansa (no idea what it looks like) flanked by green dragons rampart; top: a lion holding a globe and a sword, with an inscription (presumably on white). Guess you don't need the inscription (for 15mm) but it was LEO CON LILIS ALMANSA POMPA TRIUMPHI
Source: Sorando, Luis (2007) Banderas de la Tropas espanoles djurante la Guerra de la Independencia, in Ministerio de Defensa: "La Guerra de la Independencia (1808-1814)" a sumptuous book produced for the bicentenary.