Additional resources from the Raylib repo.

Examples/resources/shaders/glsl330/vertex_displacement.fs

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+#version 330
+
+// Input fragment attributes (from fragment shader)
+in vec2 fragTexCoord;
+in float height;
+
+// Output fragment color
+out vec4 finalColor;
+
+void main()
+{
+    vec4 darkblue = vec4(0.0, 0.13, 0.18, 1.0);
+    vec4 lightblue = vec4(1.0, 1.0, 1.0, 1.0);
+    // interplate between two colors based on height
+    finalColor = mix(darkblue, lightblue, height);
+}