Thank you. Unfortunately the colours are not the original - it started life as green.
In which case this isn't a Triumph-specific issue - the paint used could be any code from any manufacturer, but I suppose you could always hope that the previous owner chose original Triumph colours and order some samples to test based on the Triumph colour charts you can find online. Otherwise the only chance for a reasonable match would be to have your paint analysed by a paint supplier using a machine called a spectrophotometer. You'll need to remove a painted part from the car to be scanned by the machine, get the specialists to advise.
Some machines return the closest match from their pre-existing mix database of factory reproduction colours, others will generate a one-off recipe and therefore should be more accurate. A more expensive service means a more advanced machine and a better match, though for many reasons there will be no such thing as an 'exact' match so don't get your hopes up too high.
If only the people doing re-sprays and colour changes would leave a simple note of the colours they used with the vehicle paperwork it would save future owners a lot of grief, but it never happens. I have had to get complete paint jobs in the past to save endless trial and error in matching, it can be very frustrating. Good luck with it anyway.