If you are have light blonde hair- I would go for Light Brown or Taupe depending on if you want the very subtle orange undertone.
If you naturally have an orange undertone and want to avoid bringing it out, I would go for Taupe. If you don't have any orange undertone, I would go for Light Brown as the undertone won't come out.
If you have blonde hair with darker roots- Coffee
If you have red hair- Auburn
If you have light brunette hair- Coffee
If you have dark brunette hair- Coffee or Dark Brown (depending how deep you want the colour). Coffee is a warmer colour whereas dark brown is more cool toned.
If you have black hair (not natural)- Dark Brown or Black (depending how deep you want the colour).
If you have natural dark black hair- Black
The colours can also be mixed together if you want an in between as well.
*Please note that these are just a general guide and if you have any more questions, please email me at hey@amaialashes.com.au with a photo of your brows and I can give you the best advice from there.*