Hi Kathleen,
I think this is the solution that you want:
API.addSettings('injectStyle',[
'[piq-page] {border-color: #9D009D}', // frame color
'[pi-quest] .page-buttons .page-submit, [piq-page] h3 {background-color: #9D009D; border:#700070; color: white;}', // header and submit button
'[pi-quest] label {width:100%; text-align:center;}', // center stem
'[quest-select-one] button {text-align: center;}'
].join(''));
I'd note two things:
First, API.addSettings takes only two arguments, so only the first strings of css that you passed was processed (I used [].join() in order to use multiple strings.
best,
Elad