No, they do not work as in helping you lose weight. What the teas do is feel up your stomach with fluids making you feel fuller faster when you eat. Tea is full of caffeine which contributes to blocking vitamins you need for strong healthy bones. It also speeds up the heart.

Weight loss teas are mainly diuretics so you will lose water weight. It comes right back again as you drink more water.
The bad thing about many of these teas is that they dehydrate you and once you are dehydrated your body can not burn fat.
Green, white, red, and black teas are fine since they are standard teas and don't have specific additives to dry you out like one that are labeled at "diet" or weight loss". Standard teas are also full of anti-oxidants which are important and contain a small amount of caffeine that will boost your metabolism a bit.
It's best to drink tea for the taste--not for weight loss.

Yes, especially green teas, you can read more here how green tea helps in weight loss:

They just give you energy from caffeine which isn't good for you. A lot of times they give you too much energy which can speed up your heart rate too much.