SweepGradient sweepGrad = new SweepGradient(350, 350,
new int[] { Color.RED, Color.YELLOW, Color.GREEN, Color.BLUE, Color.MAGENTA }, null);
circlePaint.setShader(sweepGrad);
canvas.drawCircle(350, 350, 50, circlePaint);

<supports-screens android:anyDensity="true"/>