I\'ve got the following HTML code on a page:
Some text
Some more text!
In my .css
I\
For your literal example you'd want to use the adjacent selector (+).
h4 + p {color:red}//any that is immediately preceded by an
Some text
I'm red
I'm not
However, if you wanted to select all successive paragraphs, you'd need to use the general sibling selector (~).
h4 ~ p {color:red}//any that has the same parent as, and comes after an
Some text
I'm red
I am too
It's known to be buggy in IE 7+ unfortunately.