The unshielded radiation dose for a round trip Mars expedition with 18 months spent on the surface is roughly equivalent to the life time dose allowed for a worker in the nuclear industry. The risks are completely negligible compared to the 50% or so chances of not making it back to Earth.

https://en.wikipedia.org/wiki/Health_threat_from_cosmic_rays...

One of the first mass products of a colony is likely to be Methane and simple hydrocarbons like ethylene which can be further used to produce polyethylene, an excelent shielding material that can reduce the radiation to earth levels if applied in thick blankets.

Many concepts for permanent settlements on Mars or the moon envision tunneling under the surface to achieve radiation shielding.

Of course it would help to develop better treatments for radiation exposure.