Do you mean this part?
Right now, this part is only made in Light Aqua, so I don't think the car is buildable with that piece.
Link to bricklink
Oh, and for helping you with makeing your LDD files a reality, there is a Program that helps you find what parts are color correct, or not color correct (such as the above slope). It also gives you Bricklink links to the same part. (Excluding some parts with decorations & / or glitches!)
LDD Manager topic on Eurobricks
And, in case you didn't know, there is a even a whole LDD / LCAD section here on Eurobricks!
(Under the header "Special Intrests", and inside section "LEGO Digital Designer and other digital tools".)
Hope this helps!
Edited by Murdoch17, 21 August 2012 - 08:31 PM.