How can we pass list of spotcolor values in PDFLib set-graphics-option?

Question

I have integrated PDFLib library in the c#.net code and I have a requirement to set multiple spotcolor values in set-graphics-option method.

I tried the below code but it didn't work... Appreciate your help to fix this.

 1. optlist = "fillcolor={spotcolor {PANTONE 281 U} 1}, {spotcolor {PANTONE 15-14 C} 1}"
 2. optlist = "fillcolor={spotcolor {PANTONE 281 U} 1} {spotcolor {PANTONE 15-14 C} 1}"
 3. optlist = "fillcolor={[{spotcolor {PANTONE 281 U} 1}][{spotcolor {PANTONE 15-14 C} 1}]}"

Answer 1

It's not possible. You can only have a single color for stroke or fill at the same time.

What should be the benefit of multiple values?