Use uniforms for color

shaders/fragment.glsl

@@ -1,6 +1,7 @@
 #version 330 core
-out vec4 color;
+in vec4 vertex_color;
+out vec4 final_color;
 void main()
 {
-    color = vec4(1.0f, 0.5f, 0.2f, 1.0f);
+    final_color = vertex_color;
 }

shaders/vertex.glsl

@@ -1,6 +1,9 @@
 #version 330 core
 layout (location = 0) in vec3 pos;
+uniform vec4 uniform_color;
+out vec4 vertex_color;
 void main()
 {
     gl_Position = vec4(pos, 1.0f);
+    vertex_color = uniform_color;
 }