David.
Firstly a big welcome to the group.
You sound as if you have your project pretty well under control,
particularly concerning the paddle drives and the mixer.
I hope that you can post some photos of your model, at various stages, as we
do not have this model featured in our photo pages.
Selecting a colour scheme is a fun exercise. The tug never actually existed
in real life, so you can make it up as a tug in any of your favourite
Company colour schemes. Do you have the P.N.Thomas book, “British Steam
Tugsâ€. There are a large number of funnel/flag and colour details in that.
All the best
David.