Please advice my clothing

I am travelling to China next month first to Shanghai then Beijing and to Xi'an. Can you please advise whether it is acceptable to wear strappy t shirts or only ones with sleeves. I have long cotton skirts and pedal pusher trousers. Do these all have to be blacks and greys or can I wear white, lemon, light blue or even pink?

it is cooler in the morning and at night in Sep. I suggest that wear t shirts inside and jacket will be useful that is convenience to put on or off. you can choose any color you like, it is not cultural revolution time.