Would you explain what this poster means?

skim milk = non-fat milk

I think this sentence is written incorrectly " You mean that colored water fat people drink?"
should be "You mean that fat people drink coloured water?"

If I understand it well, it's a comparison to coloured water - refreshments.

best of luck

No, the poster is correct. You mean that colored water fat people drink? You may understand it better if I rewrite it this way.
Are you referring to that colored water fat people drink?
I have an American friend that tells me many people in the USA think that adult humans should not drink milk, and that it contributes to many health ailments, such as obesity. She also says that the indus

yes, now I got it ;p i didn't look at this that way

No, I'm pretty sure that whoever made the poster was not thinking about the mistreated cows. I think the point is that to the man in the poster, skim milk is hardly like milk at all; it's whitish but tastes more like water. And it's used mostly by fat people who want to be thin, not actually by thin and fit people.

khoff, I agree with your reasons for the poster, because I was mainly concentrating on her response. I still think my grammar concerning it is still correct.