A Lame Program

I'd take a look at the rectsoverlap function

ie

If rectsoverlap(x,y,width,height,mousex(),mousey(),1,1) and mousedown(1) then 'set colour'

Also I'd load this into a function so you get something like:

; Set up Colours
Dim Colours(8,2)
Data 255,0,0
Data 0,255,0
Data 0,0,255
Data 255,255,255
Data 255,255,0
Data 255,0,255
Data 0,255,255

For n=2 To 8
	Read Colours(n,0),Colours(n,1),Colours(n,2)
Next

; Set the default colour
SelectedColor = 2

Repeat

; Draw the buttons and change colour if the mouse is clicked
For n=2 To 8
	If colourbutton(n*20,0,Colours(n,0),Colours(n,1),Colours(n,2)) Then SelectedColor = n
Next

; Draw a block of the selected colour
Color Colours(SelectedColor,0),Colours(SelectedColor,1),Colours(SelectedColor,2)

Rect 0,20,400,40


Until KeyHit(1)


Function ColourButton(x,y,r,g,b)
	Over = False

	; Check if the mouse is over a button and set the over flag
	If RectsOverlap(x,y,16,16,MouseX(),MouseY(),1,1) Then Over = True
	
	; If the mouse is over a button set the border colour to white, otherwise make it grey
	If Over Then Color 255,255,255 Else Color 100,100,100
	
	; Draw the border
	Rect x,y,16,16,False
	
	; set the colour to the passed colour and draw the rect in the middle of the border
	Color r,g,b
	Rect x+1,y+1,14,14,True
	
	; if you're pressing the mouse and you're over the button return true else return false
	If MouseDown(1) And over Then Return True Else Return False
End Function