Styling help required

Hey all,

I need some help styling my numbered lists in posts. I want to add some padding in left margin, different colour, and increase the font size of the numbers in the numbered list but I dont know much about CSS. Ive figured out how to achieve what I want in an individual post but I need to do it for all my posts automatically. I've also figured out that I need to edit my style sheet but I have 4 of these in my theme and my eyes are going gaga looking at them.

Can some of you guys suggest code I need to add or edit and where I might put this code?

Many thanks, Larry