141 VDU 19,1,2,0,0,0 changes logical foreground colour 1 (which is initially white) to actual colour 2 which is green, and VDU19,0,5,0,0,0 changes logical background colour 0 to actual colour 5, which is magenta. ( Note: The zero at the end are for future expansion of the system.) The computer will now produce these colours until either it is switched off, the BREAK button is pressed, or the MODE is changed. These instructions to change the colours can be embedded in a program thus making it possible to alter the colours while a program is running. Here is a list of the numbers for each ‘actual colour’ that the computer can produce.
Actual colour number Displayed colour 0 Black 1 Red 2 Green 3 Yellow 4 Blue 5 Magenta 6 Cyan 7 White 8 Flashing black/white 9 Flashing red/cyan 10 Flashing green/magenta 11 Flashing yellow/blue 12 Flashing blue/yellow 13 Flashing magenta/green 14 Flashing cyan/red 15 Flashing white/black So ‘actual colour’ numbers are any numbers between 0 and 15. To make logical 3 a flashing red/cyan effect you write VDU 19,3,9,0,0,0 and here are some other examples VDU 19,1,2,0,0,0 Logical colour is green VDU 19,3,5,0,0,0 Logical colour 3 is magenta VDU 19,0,12,0,0,0 Logical colour 0 is flashing blue/yellow