>Two wires from it both the same colour.
Generates AC so the two wires need connecting to a rectifier that'll turn the AC into DC. Because it's AC, nothing to choose between the wires so that's why they're the same colour
Educated guess says the Alton is a 'permanent magnet' alternator, that produces more the faster the rotor spins, so it'll also need something to regulate the DC output depending on what's required. Usual scenario is belting along on a sunny summer's day, lights off and battery charged, with magneto ignition, the alternator spun by the engine is producing electricity but nothing's using it, the regulator will turn the excess into heat.
Usual today is to connect the alternator to the aforementioned combined regulator/rectifier. Choose carefully though, you do not want one with digital electronics, because they are more susceptible to emi (electro-magnetic interference); HT is the usual emi source, 5 KOhm plug, cap or HT lead is the usual suppression, but not on a magneto(?). Podtronics reg./rec. have analogue electronics.
Btw, when you have a reg./rec., don't try and measure its DC output disconnected from the rest of the bike's electrics, because it'll be negligible ... Reg./rec. are so-called because they "reg(ulate)" the AC first based on the DC load; if a reg./rec.'s DC output is disconnected, there isn't any DC load as far as its electronics are concerned, so it regulates by turning all the alternator output into heat.