A little help needed for newbie please.

Hi everyone, fascinating website.
I deal mainly in photo restorations but have become slightly addicted to colourising family military pictures from WW1/WW2.
This photo has me a little baffled. I’m pretty sure by the cap badge that the gentleman was in the Royal Artillery but would love some suggestions on the hex colours. I’m not sure on the date either but I will have more of those details shortly.

The colours I am interested in:
Uniform - I am aware of many different shades depending who made them in the UK.
Buttons - I’m guessing they were brass and had the artillery and crown on them.
Stripes - Never known what colours to use on these.
Hat band - Mid brown leather?

Hope you can assist.