pie chart - colours change when i want to edit it

[plantage09]

hi,

i am working on mac, ppt2008. in this version, i did a piechart with different blue colours.
i give it to a friend, he opens the presentation in ppt 2007 for pc. when he wants to edit the piegraph, it changes colours (green, blue, yellow, ...). so it doesn't maintain the colours i chose for it. how can i solve this problem? what is happening there? i need him to make changes in the data and numbers but keep the colours!

any ideas?

thanks a lot for your help!

frank