I try to find interesting and different regiments to paint too actually. I have to say, it often leads to confusion- There is usually more than one person of the same name commanding a regiment in the ECW; I am sure that I have even read that there were two Oliver Cromwells on the parliamentary side for a start.
One of my own regiments is James Carrs or Kerrs but not all the references to Carr or his regiment are for the same person. His first Regiment was never fully raised, so was disbanded and his second was drawn from or reduced into the Plymouth garrison.
Alongside this there are two other Carrs, one with a regiment on the Isle of Wight, that probably never left the Isle of Wight and another was a different Colonel! Sorry to ramble, but I imagine you come up against similar confusion. You often find that you come back to the more widely known regiments by the time of the New Model Army anyway. For instance Carrs were reduced into Ralph Weldons regiment according to Laurence Spring.
If in doubt over coat colours go for either red or blue, Brasseys 'uniforms of the Ecw' makes a case for these being the most common coat colours aside from grey or undyed wool by looking at the amounts of Indigo and Madder, imported into the country at the time.
It might be worth you trying to get hold of a copy of Laurences Springs book on the Eastern Association if you do not have it. (I have his one on the regiments of Wallers Southern Association and I find it really useful as it gives flag and coat colours when known) This should cover some of the Parliamentary regiments you are interested in- I think the Eastern Association covered Lincolnshire too.
I had hoped to put a link to this book, but a quick google tells me a new edition of the book is supposed to be published this year, so at the moment it is out of print. It should be available from the Pike and Shot society or Stuart Press later this year.