Select black. You said it was slim. I think black looks good and slim, which goes well with other accessories.

Since it is a down jacket, of course, the sweater inside doesn't need to be too thick. Well, white is good. It's ok to wear warm colors anyway (but it's not bad to show a white sweater collar)

Of course, the scarf should be a big scarf, that is, a long scarf, otherwise the long down jacket with a short scarf will be discordant and stingy. . .

Black with a red scarf is ok, of course, not too monotonous. Some lines will look less rigid, or gray scarves will look more personalized and cooler. That depends on your personality, because black, white and gray are collocations.

For the lower body, I think it should be paired with feet pants or pencil pants (dark color, of course). If you don't want to wear boots, you can change into flat-bottomed booties (preferably beige). Xixi, I like this collocation very much recently. . .

Ah, the hat. . . Just wear a slightly playful hat, but it's not too complicated. Oh, as for the hat, it's better that the basic color is similar to the scarf you choose.

In short, clothes are black, and this area occupies most of them, so other small accessories can have some bright spots, all of which are warm colors, so as not to give people a "dark" feeling.