Starlink: In the long term, SpaceX intends to develop and deploy a version of the satellite communication system to serve Mars (colony)
Boring Company: development of underground tunnels and travel for Mars colony.
Tesla Inc: development of vehicle and battery technology for Mars colony
SolarCity: development of battery technology, solar power technology, and its usefor Mars colony
SpaceX: Reusable rockets and space ships for getting to and off of Mars.
Not directly Mars-colony-related per se, but can be used as such,
Neuralink: Machine brain implants.
OpenAI: Attempting to make human-friendly AI that won't be a threat to humanity.