Snippet for generation helper texture for mip level colorization (http://aras-p.info/blog/2011/05/03/a-way-to-visualize-mip-levels/)

UnityMipColorsTexture.cs

static public Texture2D CreateMipColorsTexture()
{
    var MipColorsTexture = new Texture2D(32, 32, TextureFormat.ARGB32, true);
    MipColorsTexture.hideFlags = HideFlags.HideAndDontSave;

    Color[] colorArray = new Color[6]
    {
        new Color(0.0f, 0.0f, 1.0f, 0.8f),
        new Color(0.0f, 0.5f, 1.0f, 0.4f),
        new Color(1.0f, 1.0f, 1.0f, 0.0f),
        new Color(1.0f, 0.7f, 0.0f, 0.2f),
        new Color(1.0f, 0.3f, 0.0f, 0.6f),
        new Color(1.0f, 0.0f, 0.0f, 0.8f)
    };

    int maxMips = Mathf.Min(6, MipColorsTexture.mipmapCount);

    for (int mip = 0; mip < maxMips; ++mip)
    {
        int mipWidth = Mathf.Max(MipColorsTexture.width >> mip, 1);
        int mipHeight = Mathf.Max(MipColorsTexture.height >> mip, 1);

        Color[] colors = new Color[mipWidth * mipHeight];

        for (int index = 0; index < colors.Length; ++index)
        {
            colors[index] = colorArray[mip];
        }

        MipColorsTexture.SetPixels(colors, mip);
    }

    MipColorsTexture.filterMode = FilterMode.Trilinear;
    MipColorsTexture.Apply(false);

    return MipColorsTexture;
}