Mixing and dispensing apparatus and methods for use with, e.g., a multi-component reactive material process is disclosed. In one embodiment, the apparatus comprises a series of positive displacement pumps adapted for stacked or “piggy-back” mating to a common motive source. At least one of the pumps is supplied by a sealed and collapsible reservoir bag and flexible tubing, thereby allowing removal (and optionally disposal) of one or more complete material pathways within the system. Such a configuration allows for, inter alia, rapid colorant changing with minimal material waste, obviates the use of hazardous solvents, and increases process efficiency and worker productivity. This arrangement also obviates complex metering apparatus common to prior art systems, thereby allowing it to be as small and power/cost efficient as possible.