I have a good working relationship with the local auto paint supplier. We have purchased paint and supplies from these guys for over 30 years. They understand we (Dad, younger brother, myself) are just hobbyists and not doing paint jobs as a business. The El Camino was the 6th car we painted but, only the 2nd that was not 99A Black DuPont Centari and the first base/clear paint job.
When I explained the colors I wanted on the El Camino, Black Cherry Red over Dark Slate Gray. Being patient, humble and catching them during the less busy times of the day went a long way to getting the Black Cherry Red in the proper hue I was looking for.
Take a sample of your interior color, explain what you want, go back at a later time if they are busy, they should be able to find what you are looking for.
I also learned the advise they offer for free...9 out of 10 times will net positive results!
On another note I miss spelled the paint base in a previous posting... it is Chroma base.