WInger Colbourne has played at the Hull Ionians RFC in National 1 and for Mid Northern RFC in New Zealand.
He has received a number of honours, including the Dorset and Wilts U18 & U20, the Yorkshire U20 and the Northland NPC for two years.
“I’m looking forward to playing at Footes Lane, it always looks like the supporters come out in good numbers to see the Raiders,” said Colbourne.
“I’m very excited to be a part of this group of boys to create something special.”
Colbourne is the second signing announced by Raiders, after former Nottingham forward Josh Poullet was confirmed in May.
Raiders open their season in National League 2 East against Worthing at Footes Lane on Saturday 7 September.