As I have recently been more and more interested in minimalism I started wondering what the difference is between minimalistic and monochrome, are they the same? I would say not really.
From what I understand, minimalism is the ability to let go of all the things that are not necessary to live/dress/feel comfortable and happy. You only have the bare minimum, which can vary from person to person, and if you don't need something just get rid of it in order to avoid clutter, which can bring visual distraction and stress as you have more belongings to worry about.
Monochrome means literally "one colour", so it's not necessarily just black & white, but the use of only one colour (could be in different shades) in an outfit, design, makeup look, etc. A monochome look or home interior could be described as minimalist when the composition doesn't feature "too many" or "unnecessary" things, but that is of course, relative to each person.
So a minimalist outfit could be monochrome as well as feature different colours, patterns or textures: you might wear a plain white t-shirt with black jeans and shoes, or you could wear a patterned top, bright trousers and bold shoes but it still is only 3 pieces of clothing, just like with the monochrome look.
And likewise, a monochrome living room might have a one colour palette but be inundated with mountains of books, cushions and tiny trinkets that clutter the space and make it hard to feel relaxed when entering the room. So the fact that something is monochrome does not necessarily mean that it is minimal.
What I find quite strange, sometimes even slightly annoying, is when a person proudly calls themselves a minimalist by the mere fact of dressing in a monochrome palette in their everyday life, when they are constantly adding new items to their wardrobe or dressing room by frequently going shopping, which makes no sense.
Of course there are people that, as I mentioned, might not even dress in a very reduced range of colours, but they keep their outfits simple and work hard to maintain a closet (and life) free of clutter by implementing challenges such as "project 333" or the "5 piece French wardrobe" where you keep your closet under a chosen amount of items, investing in good quality basics and/or restrict yourself from frequent and impulsive shopping.