The only situation I can think of is that your default printer set up in ChemStation is a black and white printer (either because of how you configured it or because it's a laser printer, which is only able to print in grayscale). In that case, doing a print preview on screen will replicate what would come out in the actual printer.
To test this theory, change your default printer to the PDF printer that should have been installed with your version of ChemStation, which back then would have been the Nova Pro Print Server. Do this under File > Printer Setup. If you don't have the PDF printer available, install it from your ChemStation installation disc for B.03.01.
I would also change your report destination to File or Screen ONLY (no printer), but this is optional if my theory is correct.
Report > Specify Report:
Then, don't use the Print Preview button but instead actually output the report to screen (and/or file) by using Report > Print Report:
What should show up on the screen should now use full color scale and look like the example I posted earlier. When you choose a print destination that is inherently non-colored (or grayscale only), ChemStation changes the color pattern to line variations (solid, dotted, dashed, etc.), for as many different signals as you're overlaying, just as you noticed in your preview.
The signals will be colored based on what you chose in the Configuration Editor for this particular instrument of ChemStation (with ChemStation closed, you would start Configuration Editor and select the window of your instrument [1 or 2, for example], then change or confirm the colors in under Configure > Colors).
If Nova PDF isn't available on your installation disc, you can install any third-party PDF writers (there is a long list of freeware software that can be used here) that will allow for color PDFs.