MANILA, Philippines — The National Grid Corporation of the Philippines (NGCP) has issued red and yellow alerts for the Visayas grid and a yellow alert for the Mindanao grid due to the unavailability of some power plants. In its 8 a.m. advisory for Visayas, NGCP said the red alert will be between 5 p.m. and 10 p.m., while the yellow alert will be…