oy thats super tough .... i think since your using it day to night i would say go with black (and if you can find one) with a blue zip track!
i got the navy croc mac as my first and its perfect for day to night and its not a black but since its navy it is dark enough (for my personal taste) to be a night bag worn with almost any outfit ... but since royal is so bright (and gorgeous) its perfect for day but i dont know if i personally would reach for it at night!