Sort of… You can change all elements of a certain kind all at once, but not of different kinds; ie.,
tell application "QuarkXPress"
tell document 1
--changes only text boxes
--set the color of (every text box whose color is "Cyan") to "Black"
--change all box objects at once, including line boxes
set the color of (every generic box whose color is "Cyan") to "Black"
--change all text objects at once
set the color of (every character of every story whose color is "Cyan") to "Black"
There’s the really big difference (text or graphic elements), and I’ve not ever scripted the new goodies in Quark, like tables and perhaps other things (I’m relatively new to version 7, last seen scripting version 4). From what I can remember, at least in version 4, it got tricky with different classes of objects, especially text styles - tho a quick test above referencing a wide range of a text object with a condition, as “every character of every story whose color is…” did indeed work and I didn’t think it would (probably doesn’t in version 4).
Try variations on “every [object] whose color is…” and setting it’s color to see what works.