Matching doesn't mean identical colors, though; they just need to fall in the same hue.
A shade lighter or darker is just fine, since it doesn't relegate socks to complete anonymity but they're not screaming to be noticed, either.
It is perfectly acceptable to show some sock when you sit down.
Dress pants and chinos should never stack around the ankle. At most, you want a full break.
Some on this forum prefer no break, where the top of the pant just touches the shoe.