You're getting an infinite loop.
while (on==1)
{
ind1.FillColor = System.Drawing.Color.Pink;
}
Your code is very ugly, try this:
bool on=false;
private void start_Click(object sender, EventArgs e)
{
on = !on;
ind1.FillColor =
(on ? System.Drawing.Color.Pink : System.Drawing.Color.Black);
}
Good luck.