Is it infrared light technology? or still the green light

According to the 'How Apple Watch measures your heart rate' section in:

Monitor your heart rate with Apple Watch - Apple Support

"The optical heart sensor can also use infrared light. This mode is what Apple Watch uses when it measures your heart rate in the background, and for heart rate notifications. Apple Watch uses green LED lights to measure your heart rate during workouts and Breathe sessions, and to calculate walking average and Heart Rate Variability (HRV)."

The figure in that section shows green, red and infrared LED sensors.

According to Apple:

Apple Watch uses green LED lights paired with light‑sensitive photodiodes to detect the amount of blood flowing through your wrist at any given moment. When your heart beats, the blood flow in your wrist — and the green light absorption — is greater. Between beats, it’s less. 

Monitor your heart rate with Apple Watch - Apple Support

Apple Watch Series 8 and Apple Watch Ultra have 2 temperature sensors—one on the back crystal, near your skin, and another just under the display. While you sleep, Apple Watch samples your temperature every five seconds. This design improves accuracy by reducing bias from the outside environment.

I have found no indication that infrared sensors are used.

https://www.digitaltrends.com/mobile/apple-watch-series-8-temperature-sensor-what-it-does-how-use/

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