I have the same trouble, I'd love to take out my beige Celine Phantom or other light colored of my vintage collection but I mostly wear dark and moody clothes during winter...plus people around here would look at you wearing bright or summer fahions like you were going to a funeral in a clubbing outfit lol (I'm from Germany and winter here is like one big funeral haha)
Yes! It looks great with a neutral outfit of winter whites /creams / beiges and caramels. And it can brighten darker colors but I think it needs to be balanced with additional light colored accessories (multiple strands of pearls, light colored scarves, bangles, even beige boots, etc) so it doesn't stand out too much but instead works as part of a look.
Of course you can. As was mentioned earlier, beige goes really well with dark colors. I have my cream color Wera Stockholm tote with me, along with a bright red coat and I feel like it's a great combo to pep up this gloomy darkness.