Welcome to Autodesk Forums!
Hi Daphnee,
You have several options.
For example, you can uncheck "Plot with plot styles" option in Page Setup for the Layout you are trying to output to PDF. Then AutoCAD will output to PDF with colors, you assigned to objects (or Layers).
Or if you need monochrome output with some colored elements, then use monochrome plot style table and assign True Color to the objects you want to have in color in PDF.
Maxim
