Man pages matching name qwtcolormap in section 3:

QwtColorMap.3.en	debian 10 / libqwt-doc
QwtColorMap.3.en	debian 10 / libqwt5-doc
QwtColorMap.3.en	debian 11 / libqwt-doc
QwtColorMap.3.en	debian 12 / libqwt-doc