UNTYHOTSWomen's Sleeveless Long Sleeves Mock Turtleneck Top Basic Stretch Fitting Pullover Lightweight Slim Shirt

Im 5'7" weight 175 lbs. most weight in mid-section what size?

Is the brown a dark brown?

I am unable to find a size chart - where do I see the size chart for this product please?

I weigh 103 lbs so f I want it very tight should I get a small, or an extra small so it’s very flat but Nader a cotton T shirt?