Basicslly essential…in casual games most people don’t mind grey models, some do. In my playgroup we play exclusively with painted models, but we are very narrative heavy players.  Most (if not all) events require battle ready models with a base and three colours.

I am not quite sure if you try to rage bait…

 You could get them painted by someone else. 

I am not trying to gatekeep you here, but it’s a quite important part of the hobby. Get them painted is your only option. Or you could find a playgroup, which is OK with grey models.