title: Using gl_FragColor vs. out vec4 color?
body: <p>There seems to be a lot of ambiguity about <code>gl_FragColor</code> being deprecated.  For example, it is missing in the <a href="https://www.khronos.org/registry/OpenGL/specs/gl/GLSLangSpec.4.40.pdf" rel="noreferrer">GLSL 4.40 specification</a>, but it is included in the <a href="https://www.khronos.org/registry/OpenGL/specs/gl/GLSLangSpec.4.60.pdf" rel="noreferrer">GLSL 4.60 specification</a>.</p>
  
  <p>What is the safest, most compatible, most supported strategy?  Using <code>gl_FragColor</code> or defining a shader output like <code>out vec4 color</code>?</p>