SF_10.1, SF_10.2, SF_11.0, SF_11.1, SF_11.2, SF_12.0, SF_12.1, SF_12.2, SF_13.0, SF_13.1, SF_13.2, SF_13.3, SF_14.0, SF_14.1, SF_14.2, SF_14.3 - https://docs.sitefinity.com/for-developers-create-a-new-configuration

FontElement.cs

using System;
using System.Configuration;
using Telerik.Sitefinity.Configuration;

namespace SitefinityWebApp
{
    public class FontElement : ConfigElement
    {
        public FontElement(ConfigElement parent)
            : base(parent)
        {
        }

        [ConfigurationProperty("name", DefaultValue = "Arial", IsRequired = true, IsKey = true)]
        public String Name
        {
            get
            {
                return (String)this["name"];
            }
            set
            {
                this["name"] = value;
            }
        }

        [ConfigurationProperty("size", DefaultValue = "12", IsRequired = false)]
        public int Size
        {
            get
            {
                return (int)this["size"];
            }
            set
            {
                this["size"] = value;
            }
        }
    }

    public class ColorElement : ConfigElement
    {
        public ColorElement(ConfigElement parent)
            : base(parent)
        {
        }

        [ConfigurationProperty("background", DefaultValue = "FFFFFF", IsRequired = true, IsKey = true)]
        public String Background
        {
            get
            {
                return (String)this["background"];
            }
            set
            {
                this["background"] = value;
            }
        }

        [ConfigurationProperty("foreground", DefaultValue = "000000", IsRequired = true)]
        public String Foreground
        {
            get
            {
                return (String)this["foreground"];
            }
            set
            {
                this["foreground"] = value;
            }
        }
    }
}