Wandering Champion’s ability doesn’t trigger if you don’t control a blue or red permanent immediately after it deals combat damage to a player.

If the only blue or red permanent you control is a creature that’s dealt lethal damage at the same time as Wandering Champion deals combat damage, Wandering Champion’s ability triggers.

If you don’t control a blue or red permanent as Wandering Champion’s ability resolves, you can’t discard and draw a card. The blue or red permanent you control as the ability resolves doesn’t have to be one you controlled as the ability triggered.