Q.red Oleander with partial white leaves
I planted a red Oleander in March this year and several leaves looks like a can of white paint was sprayed over them. Why does my new red Oleander have partial white leaves as if it was sprayed with white paint? These are not white spots but have broad white and green leaves.

Is the white powdery in nature? Your plant could be affected with powdery mildew. Here is more information: https://www.gardeningknowhow.com/plant-problems/disease/get-the-cure-for-powdery-mildew.htm