Download qextserialport
The qcolorcontrol.pro file is set up to expect the qextserialport library in 3rd/qextserialport:
include(3rd/qextserialport/src/qextserialport.pri)
Grab qextserialport:
git clone https://github.com/qextserialport/qextserialport.git 3rd/qextserialport
qmake
make