When drawing a filled rectangle it is filled with the given color, the stroke parameter has no effect.
If you want to draw a filled rectangle with a border line with a different color you must draw a filled rectangle with the fill color and then draw a none filled rectangle with the line color. Note that, if the stroke value is bigger than 1, the line is centered on the rectangle coordinates. That means that the surrounding rectangle dimensions are increased by the stroke value.
In the Android documentation I found that there are three modes for the DrawRect method STROKE, FILL and FILL_AND_STROKE (with the same color). The last one is not supprted by B4A.
Best regards.