It's a little more complex than that.
Forage caps were authorised at the end of the 1820s. They were either issued in blue for line infantry or green for light infantry regiments. The early broad crowned versions had a coloured band. Red for Royal regiments, facing colour for everyone else. In the mid 1830s a simpler version with less pronounced crown was introduced which was nominally a solid blue or green but depictions of the 13th (Somerset) Light infantry show caps with a band in facing colour. Both types were used at the same time. From 1836 peaked forage caps were authorised for other ranks but these seem to be more of a feature for the 1840s. Scinde, Gwalior and the Sikh wars.
Officers forage caps were blue or green as per the men but with a black leather peak and from 1834 the band between the crown and leather peak was black for non-Royal regiments.
So yes, whilst the blue is quite dark you'll need it to be sufficiently blue to distinguish it from the black band.
Officers did occasionally wear privately purchased faux shakos. They were a light wicker frame with oil cloth stretched over them, so as to look like the actual item in the foul weather cover. Could also have the white hot weather cover. The advantage was that they were significantly lighter and more comfortable than the actual shako. So, if you fancy, you can pop the occasional officer in a covered shako.