Actually, I think most straight red cards are for 'denying an obvious goal scoring opportunity' (usually via a 'not serious foul play' foul - like most red cards related to penalties or free kicks around the area) which is a one match ban.
It's not. A straight red can be a one, two or three match ban, depending on the offence. It's violent conduct/serious foul play that is a three game ban, not the red card itself.
Two yellow card worthy offences in one match (which be a reckless challenge, taking your shirt off celebrating a...