@PaigeRosexxx I can see from your other posts that you use the TGB BIAB. I've seen many infill videos from TGB users and it seems that it's not being filed down thin enough before re-application. All of my BIAB sets have a thin clear coat as the first layer. So at the next appointment, I can file back all of the colour builder, back to the clear layer. That way you never need to try and match or blend two different colours. You just start again from the clear coat.
It's your responsibility as the nail tech to be keeping an eye on the natural nail condition, looking for lifting, greenies, nail separation etc. If you're not filing the BIAB away thin enough so that you can see the natural nail, this can be dangerous for your client's nails.
Hope this helps!