If you want to describe a person, you can use physical characteristics, but also, of course, their clothing.
Here is a small illustrated lexicon of clothing in French:
la chemise 
le pull 
le t-shirt 
la robe
la jupe 
le pantalon 
le manteau 
les chaussettes 
les chaussures 
les chaussures à talon 
And of course you can combine these clothes with colors.
But what do you say if you want to make a sentence ?
For yourself:
J’ai un pantalon bleu.
You can also say: « Je porte un pantalon bleu. » (I am wearing blue trousers.)
For others:
Elle a une robe rose.
Il a un t-shirt vert.
