It... wildly varies depending on the medium I'm using, lol. My prologue and the first chapter were all done in traditional technique, but for chapter 2 I'm switching to digital for most pages... not because it is less time-consuming, but because it costs me less (seriously, I was running out of markers every two pages while working traditionally D: ) and, given that my country is still being subjected to random lockdowns due to Covid-19, getting traditional art supplies may not be as easy in the future.
So I'd say... from three to five hours for traditional coloring and up to seven hours for digital only? ._.