label按下颜色变深

 #region label按下颜色变深
        Color m_cacheColor = Color.Empty;
        private void label4_MouseLeave(object sender, EventArgs e)
        {
            if (m_cacheColor != Color.Empty)
            {
                label4.BackColor = m_cacheColor;
                m_cacheColor = Color.Empty;
            }
        }

        private void label4_MouseEnter(object sender, EventArgs e)
        {
            if (label4.BackColor != Color.Empty && label4.BackColor != null)
            {
                m_cacheColor = label4.BackColor;
                label4.BackColor = ChangeColor(label4.BackColor, -0.2f);
            }
        }
        Color ChangeColor(Color color, float value)
        {
            float red = color.R;
            float green = color.G;
            float blue = color.B;

            if (value < 0)
            {
                value = 1 + value;
                red *= value;
                green *= value;
                blue *= value;
            }
            else
            {
                red = (255 - red) * value + red;
                green = (255 - green) * value + green;
                blue = (255 - blue) * value + blue;
            }

            if (red < 0) red = 0;

            if (red > 255) red = 255;

            if (green < 0) green = 0;

            if (green > 255) green = 255;

            if (blue < 0) blue = 0;

            if (blue > 255) blue = 255;



            return Color.FromArgb(color.A, (int)red, (int)green, (int)blue);
        } 
        #endregion