You are right. You need to find the control. Using the sender argument will help you locate the drop down without using the find control method
protected void DDLColor_Load(object sender, EventArgs e)
{
DropdownList ddlcolr=(Dropdownlist)sender;
for (int i = 0; i < ddlcolor.Items.Count; i++)
{
ddlcolr.Items[i].Attributes.Add("style", "background-color:" + ddlcolor.Items[i].Text);
}
}