Unless you are doing stage makeup, blush shouldn't look like makeup. If it is noticeable that you are wearing "blush" then it is the wrong color, or you are wearing too much of it.
The best color of blush for someone, will be the color that they turn when they get flushed naturally. (Take a look at your cheeks after exercise, etc.)
Just from what you described, I would suggest a LIGHT pink. Very soft and rosy-especially if you have cool skin with pink undertones. Don't go with brown/peach/orangey shades-because they are for more golden skin tones...and you described your skin as cool/pink undertones.
However-go LIGHT. You don't want something that looks hot pink/fuschia in the container. Think more like a soft baby pink.
Bright/obvious blush will make you look "dated". When you see yourself in the mirror, it is different than how everyone else sees you. Just like harsh blue eyeshadow and painted on eyebrows do on senior citizen ladies.
You want to go more by the photographs of you-like the one where you realized your blush wasn't working for you. It is a more accurate view of how everyone else sees you.