You are talking to a blind man who asks you to describe the colour "yellow". Write down what you would tell this man without once using the word "yellow" in your explanation. [I'm doing this for all 7 colours of the rainbow as a writing slump cheat. Read my orange, blue, red post.]
There's nothing quite like this colour to signify the peak of youth. It is certainly the one with the most vitality and life! So much so that it pours out of every pore, in so much over-abundance that it's almost wasteful. It loves to move, jump, climb, dance - ever in motion and exuberant. It simply radiants personal power and strength. But this colour is prone to over-doing things. All sour, no sweet. It is the one who would jump down the remaining 5 steps of stairs, because it simply has no patience for it. It is that one friend with crazy metabolism who cannot get fat, no matter how much he or she eats. If anything bad were to happen, it will never feel sad. Eternally optimistic and hopeful, it strongly believes that things will get better. Always. In fact, things are already great! It always think it is on the cusp of something awesome happening. Nothing signals new beginnings towards greatness more.