调整画图示例的颜色

example/src/examples/circle.js

@@ -11,8 +11,8 @@ export default class CircleExample extends Component {
     return <MapView style={StyleSheet.absoluteFill}>
       <Circle
         strokeWidth={5}
-        strokeColor='blue'
-        fillColor='red'
+        strokeColor='rgba(0, 0, 255, 0.5)'
+        fillColor='rgba(255, 0, 0, 0.5)'
         radius={10000}
         coordinate={{
           latitude: 39.906901,

example/src/examples/polygon.js

@@ -11,8 +11,8 @@ export default class PolygonExample extends Component {
     return <MapView style={StyleSheet.absoluteFill}>
       <Polygon
         strokeWidth={5}
-        strokeColor='blue'
-        fillColor='red'
+        strokeColor='rgba(0, 0, 255, 0.5)'
+        fillColor='rgba(255, 0, 0, 0.5)'
         coordinates={[
           {
             latitude: 39.806901,

example/src/examples/polyline.js

@@ -11,7 +11,7 @@ export default class PolylineExample extends Component {
     return <MapView style={StyleSheet.absoluteFill}>
       <Polyline
         width={5}
-        color='red'
+        color='rgba(255, 0, 0, 0.5)'
         coordinates={[
           {
             latitude: 40.006901,