This is a great game that tends to give people a lot of trouble. Just a quick note before getting into it: review the threads at the top of the boards. You shouldn't be posting full questions on the boards. Simply reference the PT number, section and question number(s) and perhaps a word or two (e.g. mannequin game) for clarification.
That being said, here's the basic idea:
You know that each mannequin wears one hat, one jacket and one skirt... and one of them might get a tie. Your job is to figure out the color. Here's a good basic set-up:
Hat __ __
Jac __ __
Skt __ __
For each type of clothing (e.g., hat), there are only three hats -- one of each color, red, navy and yellow. So, if Mannequin 1 gets the red hat, Mannequin 2 must wear then navy or yellow hat.
The last two rules are pretty clear and add information right into the sketch. The second rule should be notated in your sketch. The first rule is probably the most important.
The trick to this game is realizing that you already know one color that each mannequin is wearing. Mannequin 1 wears red and Mannequin 2 wears navy. It's not possible to wear all items of one color (since each mannequin must wear a hat and jacket of different colors). And, it's not possible to wear all three colors (by the first rule). That means that each mannequin must wear exactly two colors.
That leads to important information about the hat and jacket for each mannequin. Since the hat and jacket have to be different, Mannequin 1 must have a red hat or red jacket and Mannequin 2 must have a navy hat or navy jacket. This makes short work of a few questions and helps save time with many others.
HTH. If you have further questions, please let us know.