Hi,
If your circuit works, then everything is O.K. No need to worry.
1) green vs brown tracks.
It does not matter. Maybe one is tin plated the other is pure copper.
2) solder mask on vias vs not..
There may be a problem when aggressive chemical residuals are enclosed by the solder mask in the via holes..
Some recommend to open the vias ... others say closed vias are no problem
3) ground plane, copper pour
Again: as long as it works satisfactory ... no need to worry.
But copper pour is not comparable to a solid ground plane. In worst case you gate increased EMI, higher voltage spikes, increased power dissipation, crosstalk, increased long time failure rate. No chance to validate this from your photo.
Klaus