Can Mizzium Meddler steal the effect of a Renown ability?
Mizzium Meddler cannot 'steal' the Renown of the Colossus.

This is because Renown is not a targeted ability, it just effects the creature it is on.


  702.111a Renown is a triggered ability. “Renown N” means “When this creature deals combat damage to a player, if it isn’t renowned, put N +1/+1 counters on it and it becomes renowned.”


As you can see there is no mention of targeting anywhere in the rules, thus the Meddler cannot redirect it. Note that the Meddler can still target the ability, it will just do nothing since there are no targets to change.


  If Mizzium Meddler’s triggered ability targets a spell or ability with no targets, nothing happens.