Color Index ☆
Graphics statements manipulate colors indirectly through color indices, which are nonnegative integers in a certain range.
An arbitrary color can be assigned to any color index.
Color index 0 is a special one, which is the background color.
Graphics statements use color index 1 unless any color index has been specified.
This BASIC allows color indices of from 0 to 255.
Each color index has a pre-defied color as follows.
0 White, 1 Black, 2 Blue, 3 Green, 4 Red, 5 Cyan, 6 Yellow, 7 Magenta, 8 Grey, ... , 15 Silver, ...
SET COLOR MIX (Color_Index) red, green, blue
assigns the color specified by three numeric values that are between 0 and 1 to Color_Index, where Color_Index is a numeric expression.
SET COLOR MIX(15) 0,0,1
assigns blue to the color index 15.
ASK MAX COLOR m
Assigns the largest color index to a numeric variable m .
On this version, this value is 255.
ASK COLOR MIX(color_index) R, G, B
The red, green, blue strength of the color assigned to color_index is assigned to three numeric variables R, G, B.
If the color of index 2 is blue,
ASK COLOR MIX(2) R,G,B
assigns 0, 0, 1 to R, G, B, respectively .
SET … COLOR have the form of
SET … COLOR "RED"
Color names are as follows.
"WHITE", "BLACK", "BLUE", "GREEN", "RED", "CYAN", "MAGENTA", "YELLOW", "GRAY", "SILVER"
Quotation marks must not be omitted.
SET LINE COLOR RED
means setting line color through a numeric variable RED.
LET color$="BLUE" SET POINT COLOR color$