Most RIP's have the function of utilising a seperate spot colour table. This is probably one of the most under utilised functions of any RIP. They can use an installed spot colour library (you may have a pay a license fee..) or you can measure a spot colour sample directly into the RIP spot library, if you have a suitable and supported spectrophotometer. Each RIP will have a process for outputting spot colour samples that you can visually evaluate, and more importantly, measure to achieve a dE (delta E) within the agreed tolerance. Of course you will need to ensure the spot colours used the production file are recognised by the RIP spot colour library, etc.
NOTE: If you would like more information or have other questions please contact us at info@colourgraphicservices.com or at +61 (0)400 123 398.