For Taeyeon,
link Style-Sports-Wallpapers-s-E2-99-A5neism-27963359-640-960.jpg
I love her with either straight, short blonde hair or hair that is parted completely to the side and is blonde (like in twinkle).
For Jessica,
link
I love her hair when it's blonde and really curly, she just doesn't look that good with straight hair.
For Sunny,
link
and
link
I like Sunny with either short blonde hair (but not to short) or long brown hair in pigtails, instead of being down. When her hair is brown and it's down, it looks like she has to much hair and it looks messy. You could say the same about her hair being down when she's blonde but it looks worse when she has brown hair that's down.
For Tiffany,
link R9c2WLg2I/AAAAAAAAADI/VXHFxi35M_E/s1600/snsd-tiffany.jpg
For Tiffany, I like it when she has long dark hair. Her hair is just so awesome, except when its down and she has bangs. I think that if it's down, she shouldn't have bangs, and if she does have bangs, the rest of her hair should be back.
For Hyoyeon,
link
She looks good with brown hair that's down. She also looks good with blonde hair, but I think her hair looks better when she's a brunette.
For Yuri,
link
and
link
I think Yuri looks the best with dark hair that's either wavy or straight. I personally think that she looks AMAZING when she has wavy hair.
For Sooyoung,
link
and
link JeJqfywg/UWIj KXz5PUI/AAAAAAAARNQ/Tcup VJTf06Y/s1600/Sooyoung+at+SBS+Midnight+TV+Press+Conference+Wallpaper.png
Considering Sooyoung is my bias, I think she looks good in every hairstyle (except blonde). But my favorites are when her hair is down, wavy, and she has bangs(I've always wanted bangs) or when her hair is short(I love her hair in RDR).
For Yoona,
link
For Yoona, I like her hair when it's dark and long. She looks really good with straight hair or wavy hair.
For Seohyun,
link
Her hair looks really cute when its long, dark, and wavy because she looks so ADORABLE. Yeah.