Missed their location. Apologies to OP. ^^;; Perhaps an Aussie soapmaker can chime in where they like to get their micas?
Pine tar, milks (liquid), coffee (liquid), and teas (liquid) should not be added to Melt and Pour soap. Milk powder, ground coffee, and tea leaves will either not create brown or will create a speckled effect that might not be ideal (and also may be scratchy on the skin.) Cocoa powder is really the best "pantry" option for MP.
Note that FOs that cause discoloration don't always make a strong brown in Melt and Pour, either. Sometimes it doesn't discolor, sometimes it goes just slightly murky (clear base)/tan (white base), sometimes it makes a patchy brown, sometimes it gives you the perfect brown you want, etc. I've found it's very inconsistent and unreliable
Crayons may not work in MP the same way they do in cold process soapmaking and will likely create a weird texture once hardened. If it's for personal use and you're willing to risk a little bit of base to test it out, then hey, why not. Experiments are experiments.
An idea for another personal use colorant for MP is eyeshadow, as they're made mostly of mica and are skin safe. Scrape a little bit out, mix with rubbing alcohol and add to base. Note that this will likely not work for CP soap if you ever try that soapmaking method out, but it should work fine in MP.
I tend to use about 1/4-1/2 tsp mica per pound of base. Even less for my oxides and neons. A little goes a long way in MP, especially clear MP
Hope this info helps and hope you can find your dream brown~
(Edit: Added a period... whoops)