I LOVE these! I purchased the light gray and haven't noticed them being see through or show your undies. I think if you purchase this color in a size too small then visible undies may show through. These are VERY SOFT and comfortable even for sleeping. The material isn't thick so you're feeling cooler while wearing these. I purchased a size up from my normal size just in case they ran small. They fit very well. I would have to say they are true to size. I could've gotten away with my normal size instead of sizing up. I have purchased 2 additional pairs in different colors. That isn't a norm for me! I definitely recommend these!