Well your result is only going to be limited to 255, if it is a one-byte unsigned number.
To the letter this is true. However, the sensor library is supposed to return an RGB value. If the library is not doing that there is a problem with the library, as a correct RGB reading is always 0-255. The RGB value is derived from the frequency returned and there is a linear relationship between the two, so you see scaling factors built into the code OP is using.