Would it be something like this?
CLS RGB (255, 255, 255)
INK 0, 0
BOX 100, 5, 120, 25
ColorMenu()
DO
CheckMouse()
ChooseColor()
LOOP
FUNCTION ColorMenu()
PRINT "1. Black"
PRINT "2. Red"
PRINT "3. Green"
PRINT "4. Blue"
ENDFUNCTION
FUNCTION CheckMouse()
IF MOUSECLICK() = 1
DOT MOUSEX(), MOUSEY()
BOX 100, 5, 120, 25
ENDIF
ENDFUNCTION
FUNCTION ChooseColor()
IF KEYSTATE(2) = 1
INK RGB (0, 0, 0), 0
BOX 100, 5, 120, 25
ENDIF
IF KEYSTATE(3) = 1
INK RGB (255, 0, 0), 0
BOX 100, 5, 120, 25
ENDIF
IF KEYSTATE(4) = 1
INK RGB (0, 255, 0), 0
BOX 100, 5, 120, 25
ENDIF
IF KEYSTATE(5) = 1
INK RGB (0, 0, 255), 0
BOX 100, 5, 120, 25
ENDIF
ENDFUNCTION
If only you were me... Then You'd understand.