Hello,
“Grove - I2C Color Sensor” should work similarly irrespective of VCC voltage – 3.3v or 5V. The design includes a LDO and Logic level converter to adapt to two different VCC voltages.
In the example code, the raw colour information is presented in int format. Please scale it down to 0-255 by Arduino map(value, fromLow, fromHigh, toLow, toHigh) function or by arithmetic divide.
If this solution does not help, please reply with photos of your setup, experiment etc…
Thanks