The Verdict: Clear Path
Your parent needs to register as Colombian first, and then you can register through them. Both steps are paperwork at a consulate, with no age limit and no need to live in Colombia.
Colombian nationality passes from parent to child, not from grandparent to grandchild. The Constitutional Court said so in 2024 (ruling T-257 of 2024). A parent born abroad to a Colombian becomes Colombian by registering their birth, which they can do at any age, provided their own Colombian parent (your grandparent) was Colombian when they were born.
Step one, your parent: register their birth at a Colombian consulate or registry office, with their foreign birth certificate apostilled and translated into Spanish, and your grandparent's Colombian identity card (cédula) or Colombian birth registration. If your grandparent was born in Colombia before 1938, a baptism record can stand in for the birth registration.
Step two, you: once your parent's registration is done, register your own birth the same way, using your parent's new Colombian registration as proof.
This only works while your parent is alive, because they must register in their own lifetime. If they are elderly, start with their registration now.