How do you know my shade

So what I would do in this situation is online look at the shades and see if there are three or four shades that you think would match your skin tone, then go in store at Sephora and swatch them on your hand if you’re looking for something that will cover up any blemishes or redness that matches your skin tone when blended perfectly But if you’re just looking for something to brighten get one that is one or two shades later than your skin tone hope this helps!