easy ways to colour match concealer when ordering online
I try to look at Youtube videos of people (who have a similar skin tone to me) when they are testing out that product and note the shade they choose. From there I can usually eyeball my approximate shade accordingly.
I think this would be quite hard to do online. Maybe check out the MAC Studio Fix as that has tons of shades and you might find the right one.
Look up swatches online and images of people wearing the concealer and buy the shade that someone with the same skin tone as you is wearing.