McAllister will play a dual role as assistant coach and player.
Trevor Morgan, coach of Kerala Blasters said, "We are delighted that James, Colin and Saumik have signed up with Kerala Blasters. James will play a critical role in defining the team's strategy. He will work closely with the players and his insights will be invaluable in building a cohesive unit. He will also bring his vast experience on the field.
"Colin has had a very successful tenure with Charleston Battery over the last couple of years and he will add depth to our defense. I have seen Saumik evolve into a solid defense player. His presence will add flair."
James began his senior career in 1996 by signing for Dumfries club Queen of the South. He joined Aberdeen in 1999 where he spent four seasons, followed by stints with Livingston, Heart of Midlothian, Bristol City and Preston North End. James played for Yeovil town in 2012 -2014 seasons.
Irish footballer Colvin is currently on loan from Charleston Battery. He began his professional career in 2004 with Cobh Ramblers in the league of Ireland - followed by Kilkenny City, Otago United, Wilmington Hammerheads and Young Heart Manawato. Colvin has played four seasons for Charleston Battery in the USL PRO league (USA). He is the club captain and the most successful, having won two USL PRO league championships in 2010 and 2012.