I use Kate Cheek Color as my blusher during my working days. I like to use blusher mainly because I do not apply eye shadow or I apply nude eyeshadow during working days. Thus I have to highlight my cheek so that it will stand out. Besides, I like rosy cheek as well.
As you can see, it comes with a mini blusher brush (although my actual makeup blusher brush in my makeup box is quite big) and 2 shades of red / pink. When you have one shade as blusher, sometimes you can see obvious line separating your face color and the blusher, which is very un-natural. As such, the advantage of having 2 shades in a palette is for you to blend them over on your cheek for a natural blush.
Blusher is very important as it helps to give some redness to your cheek so that you dont look so pale (for fair skin people). Please remember do not go overboard with the blusher as you will look like a clown in the end, and do not choose a color that is too light for your skin. If you have dark skin, pink blusher is not recommended.
Just some natural touch to show natural blush.