[SOLVED] Button style change

I am trying to find the location of the styling code for the button on the search. When you view the component from the front end there is a search form and button to the right.

I wish to assign my own class to this button so that it fits in with my site theme.
class="readon'

I presume there is some sort of jquery UI injection of code going on as when I search for the span class that is currently being applied I can't find it.

If I wish to overwrite the current span class where do I do that? I just need to change the span class from ui-button-text to readon.

EDIT: apologies....went into wrong category...should be Crosswords