Fieldtype with multiple form elements
You have (at least) two options here:


Create a matrix block with the fields you need. That way, the user kan add one or more blocks of the type 'button' (for instance) to the page. Within button, you could have a plain text field for the link and name, a color field for the color, a number field for size, etc.
Create your own fieldtype (http://buildwithcraft.com/docs/plugins/field-types, not as easy as first option). That way you have optimal control over the way your user inputs values.


I would go with option 1.