I just used bog standard resin from the motor factors (it's what I had lying around) and used acrylic paint to tint it.
Water based paint and epoxy does not mix. That in itself will cause voids in the mixture.
If you want to tint earthy colours oxblood red / brown / near black / mustard yellow then a very safe and stable option is iron oxide red/yellow/black/brown.
They can be mixed to provide a range of colours that will match almost any wood. I mix them into the resin first to make sure the powder is whetted, then add the hardener. This also helps to decrease any heat generation created by adding powder to resin as you can let it sit before adding the hardener.
Pacer Zap is good, but the 5 minute version is very difficult to work with and starts to become stiff before 5 mins.So stick to the 30 min version.
Other options to modify the colours are Titanium dioxide white which is non toxic and also carbon black - but that is not as safe.
You can also use the remaining contents of colour laser toner cartridges to mix any colour you want, but I imagine this may be less stable over time.
The iron oxides are very cheap but if you buy all four colours, it will probably set you back over £20 when you factor in postage etc.
I am happy to send out a full set of colours free if you want, I have a surplus of these powders that I will never get through.
For any bubbles that occur in (once the water base paint is excluded) a gentle waft of a head gun should cause them to rise. Again this cannot be done with the 5 minute version easily.