Low Viscosity Epoxy Resin

It's entirely depending on the volume used, the air temp and what speed hardener you used. 

To use a stain on an epoxy project, we typically recommend using a water-based stain under the epoxy clear coat.  Be sure the stain is fully dry before coating work with epoxy.  It’s also a good idea to first test your stain for compatibility with epoxy using the cross hatch test:  Apply the stain a scrap piece of wood.  Let it dry.  Apply the epoxy over the stain and let it sit overnight.  Next day cut a tic-tac-toe image into the epoxy with a shop knife.  Place a piece of Duct tape on each of the nine squares.  Try to remove the epoxy.  If it comes off easily without any wood chards then there is an adhesion problem and will not work, but if it comes off with bits of wood attached, the epoxy is penetrating the stain and will adhere well.  Some customers have had success using oil-based stain.  Three oil-based stains that I know have been used successfully with epoxy resin in the past are Ace Hardware Great Finishes Wood Stain, Old Masters Wiping Stain and Pratt & Lambert Tonetic Interior Wood Stains.  However, the formula for a given stain can change at any time and we always recommend performing the cross hatch test on a scrap piece of wood as described above when using a new stain for the first time. 

To be FDA approved for primary or secondary food contact a finished assembly must be made with approved substances and undergo extraction testing for qualification.  MAS Epoxies 2:1 and 5:1 epoxy systems are not FDA approved for secondary food contact as they contain components that would not pass extraction testing. In case you are not familiar with the terms primary and secondary food contact, primary food contact requirements apply to food additives, and secondary food contact requirements apply to food storage containers and preparation surfaces. 

You certainly can, a lot of people like using Mixol Pigments, you can also use a small drop of acrylic craft paint, alcohol ink or mica powder depending on the desired effect you're going for

Although it's not recommended it can be done. You will need to let the enamel fully dry, if possible lightly scuff up the surface with sandpaper and then apply a seal coat or two of epoxy. Seal coats are very thing layers of epoxy that will help ensure none of the oils cause orange peel or fish eyes in the final flood coat. We do recommend doing a small scale test to see how it reacts before taking on a large scale one.