Atari 65XE Owner's Manual page 79

Run the program. A light green line goes across the top of the screen.
After plotting a pixel, use the DRAWTO command to plot a second
pixel and draw a connecting line between the two. Line 40 tells the
computer to plot a pixel at column 39, row 0, and then connect them.
Now type
DRAWTO 39,19
The command plots a pixel in the bottom right corner of the graphics
screen, just above the text window, and then draws a line to connect
39,0 to 39,19. Now type
DRAWTO 0,19
To complete the rectangle, type
DRAWTO 0,0
Now type GR.0 and list the program. Add these lines:
50 DRAWTO 39,19
60 DRAWTO 0,19
70 DRAWTO 0,0
SETCOLOR and COLOR
When you run the program, the computer draws a green rectangle
again. To brighten up the screen, type
35 COLOR 1
45 COLOR 2
55 COLOR 1
65 COLOR 3
Run the program to see a rectangle of many colors.
To change the color in a register, use SETCOLOR. You might conclude
that COLOR 1 selects the color for register 1 and that COLOR 2
selects the color for register 2. Unfortunately, that conclusion is not
quite true. Mode 3 has four registers and four colors—but the
registers are numbered 0, 1, 2, and 4, and the colors are numbered 0,
1, 2, and 3. To keep things straight, make a chart:
Color 0 = Register 4 Black
Color 1 = Register 0 Orange
Color 2 = Register 1 Light green
Color 3 = Register 2 Dark blue
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