Change Unity preview background to a nicer color!

PreviewBackgroundColor.cs

using UnityEditor;
using UnityEngine;

namespace EnhancedHierarchy {
    [InitializeOnLoad]
    static class PreviewBackgroundColor {

        private static readonly Color backgroundColor = new Color(1f, 0f, 1f); // Change this color

        static PreviewBackgroundColor() {

            Camera.onPreRender += (Camera cam) => {
                if (cam && cam.name.Contains("Preview")) {
                    cam.backgroundColor = backgroundColor;
                }
            };

            After.Frames(1, () => {
                var texture = CreateTexture(backgroundColor);

                GUIStyle preBackground = "PreBackground";
                GUIStyle preBackgroundSolid = "PreBackgroundSolid";

                preBackground.normal.background = texture;
                preBackgroundSolid.normal.background = texture;
            });
        }

        private static Texture2D CreateTexture(Color c) {
            var texture = new Texture2D(16, 16);

            for (var x = 0; x < texture.width; x++)
                for (var y = 0; y < texture.height; y++)
                    texture.SetPixel(x, y, c);

            texture.Apply();
            texture.hideFlags = HideFlags.HideAndDontSave;
            return texture;
        }
    }
}

And a few more interesting links

https://timaksu.com/post/126337219047/spruce-up-your-custom-unity-inspectors-with-a

https://github.com/Unity-Technologies/UnityCsReference/blob/master/Editor/Mono/Inspector/PreviewRenderUtility.cs