1. Open Button.skin, copy all the code, and paste it below the existing markup.
2. If VS added an ID attribute, remove it, together with its value (that is, remove ID="Button1").
3. Remove the CssClass attribute and its value, change the BackColor of the button to Red, and set
the ForeColor to Black.
4. Add a SkinID attribute of RedButton. You should end up with this code: