[Theme: Graphene] How to change "Older Articles" text and size ?

Hi everyone,

On my blog http://www.concreteboys.com I’m using the graphene theme.
It’s a great theme but I’d like to change something :
the links in the bottom of the page that enable to reach the older and more recent articles.
In my site (in french), it’s called “Articles plus anciens<<” and “Articles plus récents >>”.

I’d like if possible to change the text, the colour and the size of the police.

I’m desperatly searching since 2 weeks but I don’t have a clue where to go to change it.

I’m hoping someone could help me there.

Thanks 🙂

http://wordpress.org/extend/themes/graphene/