Background color covers text in custom control Visual Studios

Question

I have been having an issue for a while. I created a custom control based on a textbox in Visual Studios. I am trying to get the background to change color based on the text in the custom control. I haven't even got that far yet. When I change the background color of the component it seems to be in the foreground and covers the text that is written in the custom control. The current code I have is

using System;
using System.Collections;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Windows.Forms;
using System.Windows.Forms.VisualStyles;

namespace ctlNumericTextBox
{

    public class AToDTextBox : System.Windows.Forms.TextBox
    {
        public int converterRange; 
        public float voltageRange;

        public int analogToDigitalValue; //Analogue Input Value
        public int maximumVoltage; //Max Allowed Voltage
        public float dynamicVoltage; //(analogToDigitalValue/converterRange) * maximumVoltage


        public Color controlColourGood = Color.Window;

        public Color controlColourBad = Color.Red;

        protected override void OnTextChanged(EventArgs e)
        {
            base.OnTextChanged(e);
            //var displayValue = ADVAL
        }

        public AToDTextBox()
        {
            AToDTextBox customText = new AToDTextBox();
            customText.BackColor = controlColourGood;
        }
        public void SetRanges(int rangeForConversion, float rangeForVoltage)
        {
            converterRange = rangeForConversion;
            voltageRange = rangeForVoltage;
        }
        public void SetAtoDValue(int value)
        {
            analogToDigitalValue = value;
            dynamicVoltage = (analogToDigitalValue / converterRange) * maximumVoltage;
            this.Text = dynamicVoltage.ToString();

        }
    }
}