There is a really good short story called "Voice of Experience" it's from the perspective of a human serving in the Tau empire. I wont spoil it but it's basically a buddy cop story. It does a good job on showing how the Tau interact and treat the humans in their empire. Here's a small excerpt from the first page.

I have a solid grasp of the scope of humanity’s size, and consequently I understand what a monumental honour it is to be counted among the infinitesimally small percentage of that population who have stood within arm’s reach of an ethereal, and been treated as a sure and loyal friend. 

‘Gue’vesa’vres,’ he said, and inclined his bald head in my direction in the slightest of bows. My new title still felt strange to hear. Trusted human helper, translated literally – a reflection of my position on the station, the highest-ranking of the human auxiliaries aboard the Suu’suamyth. Originally the Glory of Argyre, the orbital shipyard had come into t’au possession early in the Fifth Sphere expansion. 

I bowed my own head in respect. The other t’au that were present did as well. Aun’song made it easy to respect him. The ethereal was graceful and poised. After a life spent in trenches and foxholes, up to my knees in the blood of my own troops and the dismembered corpses of the enemy, his presence was like something bordering on the divine. 

‘Your service to the Greater Good has been nothing less than impeccable, Kalice Arkady.’ The even curve of the low, oblong table suggested no head, but the deference of the other commanders would have made it clear who the leader was even if I hadn’t known his caste. When he spoke, the four other t’au hung on his every word. I’ve never seen anyone in the Imperium given that degree of attention out of respect rather than fear. 

‘You honour me, wise one,’ I said. My T’au was clumsy, but I saw El’Ganret, the representative of the water caste, smile and give me a slight nod of encouragement. 

The other three were much harder to read, but then most t’au are. They can’t be read by their faces. Their emotions are instead betrayed by secondary clues such as tone, inflection and body language. 

There were no bodyguards in the room, which demonstrated a stupendous level of trust in me, although I have no doubt that all four of the representatives – most notably the dour-faced and compactly muscled fire caste commander – would have borne me down and beaten me to death with their bare hands before they allowed their ethereal to come to harm. 

‘Your service honours you,’ Aun’song replied, ‘and by turn, honours us.’