paint-like help

The line:

 entitycolor active, red, green, blue

changes the color of the object that is refered to with the 'active' variable.
So if you say:

active = car

then the line will change the color of the car.
However, after you say:

active = bws

the line will change the color of bws.

The second part is a bit harder to explain. It deals with arrays, which are defined with a Dim (=dimension?) statement.
Dim allows for multiple variables to be refered to, using a number as an index.
So, if you create an array:

Dim x(10)

Then, after that, you can use x(0), x(1), x(2) .. etc x(10).
In this matter, "sel" is a number that is filled in between the brackets. So, if sel = 1, then the line

entitycolor active, red(sel), green(sel), blue(sel)

will become

entitycolor active, red(1), green(1), blue(1)

And if sel = 2 then the line will be

entitycolor active, red(2), green(2), blue(2)

Maybe the best explanation will be a working example:

Graphics3D 800, 600, 0, 2
SetBuffer BackBuffer()

;create camera
camera = CreateCamera()
PositionEntity camera, 0, 0, -10

;create array to store colors
Dim red(5)
Dim green(5)
Dim blue(5)

;initialize 6 separate colors
For i = 0 To 5

	red(i) = 255
	green(i) = 255
	blue(i) = 255
	
Next


;create 6 objects
object0 = CreateSphere()
PositionEntity object0, -7, 0, 0

object1 = CreateSphere()
PositionEntity object1, -5, 0, 0

object2 = CreateSphere()
PositionEntity object2, -3, 0, 0

object3 = CreateSphere()
PositionEntity object3, -1, 0, 0

object4 = CreateSphere()
PositionEntity object4, 1, 0, 0

object5 = CreateSphere()
PositionEntity object5, 3, 0, 0

;select object0
activeobject = object0
;select color 0 -> red(0), green(0), blue(0)
selection = 0

Repeat

	;use keys 1-6 to change object
	If KeyHit(2) Then activeobject = object0: selection = 0
	If KeyHit(3) Then activeobject = object1: selection = 1
	If KeyHit(4) Then activeobject = object2: selection = 2
	If KeyHit(5) Then activeobject = object3: selection = 3
	If KeyHit(6) Then activeobject = object4: selection = 4
	If KeyHit(7) Then activeobject = object5: selection = 5
	
	;get color of current object
	r = red(selection)
	g = green(selection)
	b = blue(selection)
	
	;apply color to current object
	EntityColor activeobject, r, g, b
	
	;use cursor keys to change color
	If KeyDown(203) Then r = r - 10
	If KeyDown(205) Then r = r + 10
	If KeyDown(200) Then g = g - 10
	If KeyDown(208) Then g = g + 10
	
	;put r,g,b back into array
	red(selection) = r
	green(selection) = g
	blue(selection) = b

	RenderWorld
	Text 0, 0, "activeobject = " + activeobject
	Text 0,12, "red = " + r
	Text 0,24, "green = " + g
	Text 0,36, "blue = " + b
	Text 400, 50, "use cursor keys to change color", 1
	Text 400, 70, "use 1-6 to select object", 1
	Flip
	
Until KeyHit(1)