Count telephone number tokens within field

Hi,

I would like to add the counter of the telephone number within the form and give color:red.

Is this possible you think?

https://contactform7.com/max-min-length-options-and-character-count/

example on: https://www.ebicus.com/nl/vacatures/oracle-integration-consultant/ (scroll down page)

I tried to include [count Telefoonnummer down] within the [tel telephone] but that does not work

hopefully someone knows or tried this before