For my job, I've written a Macro that does exactly that. Currently, it uses the variables for a specific illuminant (which I intend on expanding), but automatically colors the cells next to the LAB values (which I intend on changing as well) with the corresponding RGB colors. If still interested, please take up contact with me.
Edit: Here is the link to my GitHub with the UserForm:
https://github.com/Mister-Dinky/LAB-to-RGB: An Excel UserForm to convert CIELAB values to RGB