Exclude multiple nodata points from raster in ArcGis.

[UMARARSHAD]

I brought in the ECW raster file captured by the drone into ArcMap and performed georeferencing using ArcGIS Online imagery. Initially, I designated the white background in my raster file as no data by assigning the RGB values of 255,255,255. However, I discovered later that the background comprises various colors, including 254,255,253. How can I exclude both the previously designated color and this newly identified color to enhance the cleanliness of my image?