>> How can I toggle the source(s) on/off through Midi as at the moment I need to hold the pad for the grid to remain active?
When you select the midi note, there's a toggle option. It automatically generates the formula for you.
Just for your information, the formula looks like:
toggle(onbeat(midi.note(1,10)))
It returns either 0% or 100% and it should work with your touch sensitive pad.
>> How can I create pure Red, Green and Blue values with the HSL model?
Pure red is: hue = 0, saturation = 100%, intensity = 50%
Pure green is: hue = 120, saturation = 100%, intensity = 50%
Pure blue is: hue = 240, saturation = 100%, intensity = 50%