very high heat (~200C) for a very short period of time turns on yellow (not long enough to turn on magenta and cyan)
medium heat (~150C) for a medium time turns on magenta (not hot enough to turn on yellow, not long enough to turn on cyan)
lower heat (~100C) for longer period of time turns on cyan (not hot enough to turn on yellow and magenta, long enough to get down to cyan layer and turn it on).
Combinations generate full gamut of color.
^
unfortunately it's too late for me to try it out again, no paper left.
but anyway, thank you for your tip. :)