The problem here is that you haven’t specified a color space, so PsychoPy’s using its default color space, which is RGB between -1 and 1.
With 1 being the maximum, [25, 0, 0] is maximum red, medium blue and medium green, which is why the color isn’t changing.
If color space isn’t specified for a stimulus it uses the color space of the window, so you can leave the Rect as is and just add colorSpace = "rgb255" to where you create the window (visual.Window(...))