Always use blue for book 1 middle sphere images

Resolves #1492

Author: hollasch

books/RayTracingInOneWeekend.html

@@ -3159,7 +3159,7 @@
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
         auto material_ground = make_shared<lambertian>(color(0.8, 0.8, 0.0));
-        auto material_center = make_shared<lambertian>(color(0.7, 0.3, 0.3));
+        auto material_center = make_shared<lambertian>(color(0.1, 0.2, 0.5));
         auto material_left   = make_shared<metal>(color(0.8, 0.8, 0.8));
         auto material_right  = make_shared<metal>(color(0.8, 0.6, 0.2));
 
@@ -3238,7 +3238,7 @@
     int main() {
         ...
         auto material_ground = make_shared<lambertian>(color(0.8, 0.8, 0.0));
-        auto material_center = make_shared<lambertian>(color(0.7, 0.3, 0.3));
+        auto material_center = make_shared<lambertian>(color(0.1, 0.2, 0.5));
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
         auto material_left   = make_shared<metal>(color(0.8, 0.8, 0.8), 0.3);
         auto material_right  = make_shared<metal>(color(0.8, 0.6, 0.2), 1.0);
@@ -3410,8 +3410,8 @@
 
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
     auto material_ground = make_shared<lambertian>(color(0.8, 0.8, 0.0));
-    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
     auto material_center = make_shared<lambertian>(color(0.1, 0.2, 0.5));
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
     auto material_left   = make_shared<dielectric>(1.5);
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
     auto material_right  = make_shared<metal>(color(0.8, 0.6, 0.2), 1.0);