Are you under the watch of anyone from Heritage? We did a massive reconstruction at our grade 2 house so she was already watching like a hawk and yes she wanted say in the doors. We couldn't change our actual door as its very old and she did want to know our colours but didn't step in our way, thankfully. Although they were very traditional and boring. We have been told that if we make any changes they can be forcefully removed or changed. The usual 7yr rule does not apply to listed buildings. If at any point in the future you are found to have flouted any rules you risk action being taken against you. Massive fines too, apparently.
Your best bet is to invite your conservation officer to meet you at the property to discuss this. You can then have a casual discussion. In my case I wanted to change from white to country cream ( which nearly every other property in the street had already done) he happily agreed and got me to email for confirmation.