Assertiveness and wearing the wrong shirt...

I don't often get caught off guard while working my second job, but once in a while someone speaks to me so brazenly, intentionally or not, that I am truely taken aback.
Last night was one of those times. After I rang the doorbell at one house where I was trying to deliver a court order, a woman opened the door and said "I'm not interested!" as she picked up a parcel from the porch. I replied "Excuse me?" The woman said "I am not interested in whatever you have!" as she waved at my clipboard. Perplexed, I responded "So you aren't interested in the fact that I am a Constable and I am here with court papers?" She looked up, her jaw dropped just a fraction of a second before her hands covered her mouth, and after regaining her composure she said "Oh my gosh! I am so sorry! I thought you were with the dish network!"
Apparently, some sales reps from Dish Network have been out working that particular neighborhood pretty hard. She said that she had been deluged with salesmen over the last few weeks, with three coming within the last few days. They have for the most part been wearing light colored polo shirts with ID's hanging from their necks. I had just happened to wear a light colored uniform shirt and when she saw that in combination with my badge hanging from my neck, she assumed that I was just another salesman. (To be fair, the sun was right at my back...)
I gave her the papers I had for her, and we chatted for a few minutes. She kept apologizing, and I kept reassuring her that I was not upset. I did however give her a few tips on dealing with solicitors in the future.
From now on I'm sticking with Blue or Black uniform shirts in that area.