Even if you do go for a more neutral-tone foundation, it's still useful to know your undertone, not just for foundation purposes, but also for choosing other types of makeup, like
Soh also suggests taking photos of yourself in bright daylight to see which tones (warmer or cooler, both in clothes and makeup) suit you better. "It also helps taking photos standing next to other people with distinct yellow or blue undertones," he says. "A friend might be the same tone as you but have a warmer (tanned) or cooler (pinky or rosy) undertone. You might see to have a slightly green cast which would mean you have an olive tone."
And sometimes you might just have a neutral tone after all. Martin says if it's challenging to noticing your undertone straight away, it's more than likely that you're neutral. He recommends neutralizing any redness around the nose or flushed cheeks with either a corrector or warm undertone to counter the redness.