Let's say a textbox should have the first paragraph in orange, and the rest in 
black.

ooimpress supports the use of graphic styles for the entire text box, and can 
apply character formatting to a run of text, but it apparently doesn't support 
paragraph styles. OK for this as a GUI choice, but still ooimpress should be 
able to load XML files that use paragraph styles to define formatting.

Example:
  <draw:text-box>
    <text:p text:style-name="P5">This text orange</text:p>
    <text:p text:style-name="P1">This text black</text:p>

Currently the paragraph styles are ignored, which kills interoperability with 
other OpenDocument applications like KOffice's KPresenter.