Your hair is red. Your eyes are blue. Explanation: "Your" indicates ownership. In other words "your" means "belonging to you". Do not confuse with "you're", it is entirely different "you're" means...
An is used before all words beginning with a vowel sound. The word having the vowel sound may begin with a vowel or with a silent h as in an honor. Similarly, a word may start with a vowel, but not...
Their cat was there on the sofa. There are pictures hanging on their wall.(*Their is the plural possessive, of or belonging to them. There means location or existence.)