Hello Daniel!
All major ink manufacturers have mixing systems. They generally use certain mixing colors or a pigment and base and the components are blending together following formulas to create pantone colors.
Wilflex has 3 mixing systems. They have MX, PC Express, and Equalizers. The MX is a finished ink mixing system, meaning the inks can be used directly out of the bucket. The Equalizers are a balanced colorant and base mixing system - so you need to mix them with a base to make a color. THe PC Express sytem is a pigment concentrate and base mixing system; it also has to be mixed at a certain ration following formulas to acheive the correct color and make finished ink.
I have attached a PDF of the Wilflex Systems.
Wilflex also carries Pantone Guides, which can be purchased through a distributor. I have attached a distributor listing.
You can also purchase a Pantone Guide via the pantone website. Most people use a standard Coated guide. This simply means the chips are coated and appear a bit more intense.
I think Mixing Systems are GREAT! (as you can probably tell

)
Thanks,
Erin