Artifact is a card game by Valve.
Hero order is the order in which your heroes come to play.
Heroes with the strongest stats go to 3 first spots. 2 of color X, 1 of color Y.
4th should be color Y, so you can place it in two possible lanes for the maximum color spread.
5th hero stats or color doesn't matter as much, can be even third "late game" color Z.
Focus on the 3 and 4 cost cards of color X you have hero majority on the first 3 spots.
Prefer to play heroes with passive effects first, and heroes with active abilities later.