How to change the theme of Office 2013

Thanks Michael.  I am aware of that.  However, the three themes available are  all pale and very bland.  More contrast is what I would like to see back in Office. Cheers.

The Office 2013 interface is an abomination by definition... "greatly disliked or abhorred ", "

intense aversion or loathing; detestation."

Either no contrast or too much contrast; devoid of color; devoid of any visual separation or depth..

Who thinks that, under normal roomlight, a medium-blue highlight over skinny medium-grey type on a medium-medium grey background is at all visible (much less when the sun is streaming in floor-to-ceiling office windows)?

Of course the ribbon hasn't gotten any better... and why, in the reading pane, does the message just disappear into white? How about some indication of separation between the header and the message?

For partially sighted people the "whiteness" of the sceen overwhelms what little sight they have got. The lack of colour difference between the different parts of the working area means they cannot see the menus etc quickly or easily - this is seriously slowing them down and reducing the amount of time they can actually work! I have good eyesight and I have to keep taking a break! Please bring back the ability for people to customise their own work space within each of the office applications - it will make you a lot of friends!

Please give us some color options, this is ridiculous.  Had office 2013 installed and within 1 minute was already in the options changing the color, and none of the choices were acceptable.  Then the next thing I did was look for answers and here I am along with everyone else, wondering what the heck were the developers at Microsoft thinking.  I have used Microsoft office since its inception, this release is a color disaster.