yes IMHO this is a nice addition. I did this on my trailer this summer. Magnets are available in either black or white.
A couple of hints:
1) I didn't remove the existing latch to hold the door open, no real reason to remove it and it still is there if needed.
2) put the magnet in the middle top of the door, not a side. Keeps forces most equalized to help keep the magnet holding the door open
3) for best adhesion use the 3M VHB tape AND the adhesion promoter. The adhesion promoter is very important. vastly increases the adhesion and minimizes the risk the adhesive doesn't adhere with full force. The adhesive poromoter is available from auto parts store or amazon. I just buy a box of the adhesion promoter wipes on amazon.
here is a link
https://www.amazon.com/3M-Adhesion-Promoter-Sponge-Applicators/dp/B01G2BHLG6/ref=sr_1_4?ie=UTF8&qid=1542906373&sr=8-4&keywords=3m+automotive+adhesion+promoter
you can also get it as a box of 50.
2011 Keystone Outback 295RE
2004 14' bikehauler with full living quarters
2015.5 Denali 4x4 CC/SB Duramax/Allison
2004.5 Silverado 4x4 CC/SB Duramax/Allison passed on to our Son!