Thighs

I have thick thighs and I learned from all the fashion websites that Boot cut/ flared type of pants could balance out my body. However the flared type of pants are not in right now. The straight cut and skinny type, which is quite fashionable, does not do any good for my thick and short thighs. I am not sure what type of pants I should wear right now.

Another thing is about the colour, I wear black pants most of the time to slim out my body, but I do like to wear white pants. I just can't find the right material for this white pant in order to make my thigh look slim, and thick enough not to show my panty lines.
What do you suggest?

Be sure to look for flat front, straight leg trousers, not 5 pocket pants. In trousers, the legs begin immediately below the waistband. In 5 pocket pants, there's a strip of horizontal cloth sewn in in the back just below the waistband, and above the beginning of the legs.
Consider wide cuffed pants if you aren't too petite in height; or a wide sweep hem without cuffs if you are. To be certain that the pants are straight leg, not tapered, fold the hem up over the thigh, and see that they are the same width. If the trousers aren't too tight at the thigh, and they fall straight (or widen) at the hem, you will get a very flattering look. As an alternative, try some palazzo pants (with really wide legs) and see how they look. Be careful, whatever pants you wear, that they are the right length (Not too short! They should cover most of your shoe!) and that the hem is angled properly for your shoes as well. Consider high wedges or heels to give your legs some added length.

About the panty lines, you can avoid them under white pants with flesh tone (not white) underwear, in a "boycut" style.