It's a good idea to adhere to the convention that sensors should be connected to the numbered ports as follows:
1= touch 2 = gyro 3 = color 4 = ultrasound or infrared
The gyro sensor is not included in the 'home' version of the EV3 kit, but is available for purchase as an optional extra.
Important: Keep the gyro sensor and EV3 very still when connecting the cable and during start-up of the EV3, otherwise the gyro sensor reading will wander away from the correct reading.
When in color recognition mode the sensor is very fussy about colors - 'official Lego colors' (i.e. Lego brick colors) work best.
The ultrasonic sensor is included in the 'education' version of the EV3 kit but not in the 'home' version. The home version contains instead an infrared sensor which can be used to measure distance ('proximity') VERY approximately and it can therefore be used in place of the ultrasound sensor - see the next exercise.
The education version of the EV3 kit does not contain an IR sensor and therefore there are no exercises in the education version that use the IR sensor. This exercise, then, is for those of you that DO own the IR sensor (because you bought the home edition). This exercise is identical to the previous exercise except for the different sensor.