$01800f00: MOVE #$0f00,color01
$3003FFFE: WAIT x=3,y=48 (mask=$FFFE)
$018000f0: MOVE #$00f0,color01
$3203FFFE: WAIT x=3,y=50 (mask=$FFFE)
$0180000f: MOVE #$000f,color01
$3403FFFE: WAIT x=3,y=52 (mask=$FFFE)
Try adding something like this.
0180 is the background colour, were the FFFE is the wait raster command.
this small example changes the background colour at raster 30,32 and 34.
0f00=red
00f0=green
000f=blue
(Oh, I assume the : after the commands is comment?)
