It's definitely just a personal preference but the value of these accessories alone (usage or resell) gives your MBP even better value overall, which in my opinion should be the priority. But for sure, the colour can be more important for somebody and it's ok
I picked up a new MBP 15" 2018 in Silver because I like it more, especially in different lightning conditions. However, Space Grey definitely look spectacular in specific light. This alone made my decision even harder, especially after so many years with the Silver models.
My friends are 50:50 on this, so I think it's just up to you and not somebody else. Make a decision based on your priorities. If you want to grab attention, get the Space Grey as it has that "new" appearance. However, for me the Silver looks much more premium.
Remember, until it is a your choice, it's a good choice
Good luck!
Edit: Oops, now I see you can get those accessories from your brother. That alone should make you pick up the colour you like until you won't be sitting at your desk with those accessories for more than a 51% overall spent with you MBP