There is a few ways to use siril the easiest way is to use scripts, so lets assume you dither like me so all you need is light frames ,Bias frames and flat frames ,create a folder and name it for your target ie M13 ,now open folder and create three folders name them Biases ,Flats and Lights , now put relevant files into these folders ,> open siril and change the working directory (bottom right) to the folder containing M13 now go to scripts choose DSLR processing No Dark ,thats it ,off it goes ,you just choose the script for your files so if lights darks biases flats used choose DSLR processing though remember to create a folder Darks , or you can use sirilic no need to open siril tutorial here http://download.startools.org/Siril with Sirilic.pdf back to your no colour i assume you have debayer ticked/unticked