You should wear a nude bra (or one that’s close to your natural skin color when wearing a white top. Don’t wear a white bra under a white shirt because it will show through.
Do wear a molded bra under a form-fitting top to give yourself a smooth appearance.
Do wear a backless bra when wearing a sexy backless top. When wearing a backless top you want to highlight your back not your bra.
The VPL (visible panty line) is always a don’t. There are a number of panty options available to eliminate the VPL such as a G-string, thong and seamless panties.
Wearing body shapers such as Spanx is always a do. Body shapers can help emphasize body parts you like and de-emphasize body parts you don’t like. Just make sure your body shaper doesn’t extend past your actual clothes such as in the photo on the right.
Style Spy 
Thanks for posting this. Does the first do/don’t also apply to nude slips and white skirts too? Or can white slips under white skirts be fine?
Hi Kate, yes this would apply to all white garments including skirts and dresses. When wearing white colored clothing, it’s best to wear skin-toned undergarments (bras, slips, underpants) to ensure that nothing peeps through to draw the eye to the wrong place. When shopping for nude colored undergarments, look for ones that are as close to your skin color as possible.