Black socks are perfect, but colorful ones are equally great. Look at colorful socks as an accessory, not necessity.
Dressing up is less about the “do nots”, and more about the opportunity to wear something that complements your outfit. For starters, over-the-calf socks are best as they hide leg hair when you cross your legs.
Next, make sure your socks match your pant hem, not your shoes: This allows your silhouette to stay long and clean without their being a break in the color. As to accessorizing, wear something cool. Bright socks, colorful socks, and patterned socks will all add interest to your outfit. Make a statement; ditch the plain blacks and wear something that makes you stand out.