Gist for https://github.com/menny/menny.github.io/blob/master/_posts/2013-12-09-branding-edge-effect.md

brandGlowEffect.java

static void brandGlowEffect(Context context, int brandColor) {
    int glowDrawableId = context.getResources().getIdentifier("overscroll_glow", "drawable", "android");
    Drawable androidGlow = context.getResources().getDrawable(glowDrawableId);
    androidGlow.setColorFilter(brandColor, PorterDuff.Mode.SRC_IN);
}

brandGlowEffect_full.java

static void brandGlowEffect(Context context, int brandColor) {
      //glow
      int glowDrawableId = context.getResources().getIdentifier("overscroll_glow", "drawable", "android");
      Drawable androidGlow = context.getResources().getDrawable(glowDrawableId);
      androidGlow.setColorFilter(brandColor, PorterDuff.Mode.SRC_IN);
      //edge
      int edgeDrawableId = context.getResources().getIdentifier("overscroll_edge", "drawable", "android");
      Drawable androidEdge = context.getResources().getDrawable(edgeDrawableId);
      androidEdge.setColorFilter(brandColor, PorterDuff.Mode.SRC_IN);
}

EdgeEffect_ctor.java

public EdgeEffect(Context context) {
    final Resources res = context.getResources();
    mEdge = res.getDrawable(R.drawable.overscroll_edge);
    mGlow = res.getDrawable(R.drawable.overscroll_glow);

EdgeEffect_draw.java

public boolean draw(Canvas canvas) {
...
    int glowBottom = (int) Math.min(
            mGlowHeight * mGlowScaleY * mGlowHeight / mGlowWidth * 0.6f,
            mGlowHeight * MAX_GLOW_HEIGHT);
    if (mWidth < mMinWidth) {
        // Center the glow and clip it.
        int glowLeft = (mWidth - mMinWidth)/2;
        mGlow.setBounds(glowLeft, 0, mWidth - glowLeft, glowBottom);
    } else {
        // Stretch the glow to fit.
        mGlow.setBounds(0, 0, mWidth, glowBottom);
    }
    mGlow.draw(canvas);
...        

Thumbs up for PorterDuff.Mode.SRC_IN

Updated the gist. Thanks.