The project sometimes does not recognize me a class

I have a class that I use to generate the custom buttons of my project in winforms, I simply define the font..color and in this way I use this custom button in all my forms.

The structure of files and directories that I have is this, within the solution I have this class

Content of the controls classCustomized

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace controlesPersonalizado
{
    public class botonColor : Button
    {
        private static event EventHandler ColorCambiado;
        private static Color fondo = Color.White;
        private static Color colorfuente = Color.Black;

        public static Color Fondo
        {
            get
            {
                return fondo;
            }
            set
            {
                fondo = value;
                if (ColorCambiado != null) ColorCambiado(null, EventArgs.Empty);
            }
        }

        public static Color ColorFuente
        {
            get
            {
                return colorfuente;
            }
            set
            {
                colorfuente = value;
                if (ColorCambiado != null) ColorCambiado(null, EventArgs.Empty);
            }
        }

        public botonColor()
        {
            Fondo = fondo;
            ColorFuente = colorfuente;

            this.BackColor = fondo;
            this.ForeColor = colorfuente;
            this.Font = new System.Drawing.Font("Microsoft Sans Serif", 9F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(0)));

            ColorCambiado += botonColor_ColorCambiado;
        }


        private void botonColor_ColorCambiado(object sender, EventArgs e)
        {
            this.BackColor = fondo;
            this.ForeColor = colorfuente;
        }
    }

}

The problem I have is that sometimes (not always) when I open the form in design mode I get this error

I leave you some captures of the properties of the file

Sometimes recompiling the whole solution, closing the form and reopening it works but sometimes not. What can I do?

Thank you,