Sealed Knot info is useful although I have seen contradictary info in other sources and have heard that some of their uniform choices are conjectural.
After the relief of Gloucester, some of those in Essex's Parliamentary Army are believed to have been issued with new coats that were grey (English Civil War Flags and Colours: English Foot v. 1 (E.C.W. flags and colours) by Stuart Peachey and Les Prince) so coat colours probably changed for some units during the duration of the war so that makes this subject more complicated. I believe the baccus info is based on that in the above mentioned, book. I am no expert though.
If no colour is known for a unit you fancy doing, it is probably safest to do them in Red or Blue as I have read that large quantities of Indigo dye were being imported into Bristol during this time, and Madder was easily available too. Steer clear of black coats though it is an absolute no no, as black dyes were very very expensive.

