The Eclipse Payment Service app can be customised by editing various colours. The way this works is by setting your colours as a JSON object and appending them to the URL that is returned by the completionUrl as a parameter called style.

private String getStyle() throws JSONException { 
    JSONObject o = new JSONObject();
    o.put("backgroundColor", "#ECE5DD");
    o.put("textHighlightColor", "#25D366");
    o.put("textColor", "#000000");
    o.put("buttonColor", "#075E54");
    o.put("buttonTextColor", "#ffffff");
    o.put("iconColor", "#075E54");
    o.put("actionBarColor", "#075E54");
    o.put("actionBarTextColor", "#ffffff");
    o.put("secondaryButtonColor", "#25D366");
    o.put("schemeLogos", "M,V,A");
    return "&style=" + URLEncoder.encode(o.toString());

The scheme logos are used to remove or add the Mastercard (M), Visa (V) or Amex (A) logos.