Change Piechart result colours?

Hello,
I am wondering if there is a way to change the result colours for the google pie chart?

Currently they are a grey.. I am presuming #555 or close to that. I would like to have them either black or white (#000 or #ddd- okay, not quite white, but close enough)

I am looking at the charts.php, and I think I see where it pulls the results however I am unsure what to add or change.

My current-
.../helpers/charts.php, line 48:

<img id="pieimg" src="http://chart.apis.google.com/chart?chs=<?php echo $dimentions; ?>&amp;chd=t:<?php echo $data; ?>&amp;cht=p3&amp;chl=<?php echo $labels; ?>&amp;chco=<?php echo $tcolors;?>&amp;chf=bg,s,7A756B" 

Am I on the right track? I am so lost here.

Thank you very much!
Sarrene'