Can I safely integrate 3,3v sensor with 5v Arduino UNO? How? I plan to use Adafruit's RGB sensor with Arduino working as a RGB controller running on 5V. In my location, the 5V-compatible version of the sensor is not available.

There is a 3,3V pin on my Arduino board. Can I use it to power the sensor, or will the data pins (which are rated 5V) still burn it? 

The TCS34725 chip uses I2C communication, which arguably would still be compatible with the 5V (http://playground.arduino.cc/Main/I2CBi-directionalLevelShifter)

I am still very new to the electronics, and I don't feel confident enough to build my own level converter, and sadly, no converters advertised on arduino.cc are available in my country (Poland).
If you need I2C the best solution is go for a logic level converter based on BSS138 mosfet or similar. I've used a few and they never let me down. Examples: Sparkfun have this https://www.sparkfun.com/products/12009 and Adafruit http://www.adafruit.com/products/757



if you have also a few transistors available, you can make your own homemade solution till you get something more robust, according to arduino page: https://playground.arduino.cc/Main/I2CBi-directionalLevelShifter


(source: arduino.cc)