fix colors and launch screen

Signed-off-by: Andrey Shovkoplyas <motor4ik@gmail.com>

android/app/src/main/res/layout/launch_screen.xml

@@ -2,13 +2,8 @@
 <FrameLayout
         xmlns:android="http://schemas.android.com/apk/res/android"
         android:layout_width="match_parent"
-        android:layout_height="match_parent">
-
-    <ImageView
-            android:layout_width="match_parent"
-            android:layout_height="match_parent"
-            android:scaleType="centerCrop"
-            android:src="@drawable/launch_screen"/>
+        android:layout_height="match_parent"
+        android:background="@color/background">
 
     <ImageView
             android:layout_width="wrap_content"

android/app/src/main/res/values/colors.xml

@@ -1,6 +1,6 @@
 <resources>
     <color name="primary">#4360df</color>
-    <color name="primary_dark">#5c6bc0</color>
+    <color name="primary_dark">#FFFFFF</color>
     <color name="accent">#5c6bc0</color>
     <color name="background">#FFFFFF</color>
 </resources>