Have I found a bug in QPC2?

[pjw]

Floating point values are rounded on PRINT, so you don't get the real value if you just type in what you see. Apart from that why don't you just do "red*65536+green*256+blue", all components 0..255.

Alternatively, since COLOUR_24 implies SMSQ/E, just use the hex: INK#ch; $FFFF00 <-set yellow ink. You can even compile these values directly with Qlib these days.