you've abstracted your code so much it's not possible to determine your error. i can just say that code would cause compiler errors if it were your real code.
anyway, use the trace function to debug.
and watch out for this: changeColor.color = e.currentTarget.text;
assigning a textfields text property may be problematic even if you use the correct reference to a textfield. ie, check:
trace(e.currentTarget.text);
trace(isNaN(Number(e.currentTarget.text)));
that aside you might find it easier, if you're dragging and dropping movieclips, to assign a property to each movieclip that indicates its color. eg:
firstRectangle_mc.colorVar=0xff0000;
//etc
you can then use the colorVar property of the dropped movieclip to assign a color your droptarget's colorTransform.