Not necessarily - there's always going to be a color or style that none of us have seen before, and we need to see more than an odd color to say something's fake. We need to see the details of the bag, the creed and the serial number first. Color can be a red flag but it takes solid details to prove that something's real or fake. And don't forget, someone may have just re-dyed the bag a non-stock color. I've seen at least one vintage leather bag that was re-dyed in a pastel color but the dye job was pretty obvious.
Remember too what I said in my first answer - there can be a HUGE difference in the actual color of a bag and what comes out in a digital image (older chemical-and-paper photos were actually a lot more accurate and consistent in showing colors correctly). Too much or too little lighting and whether the lighting is natural daylight, direct or indirect sunlight, flourescent, incandescent, all make a big difference. And most phones especially older ones just are NOT designed to be accurate cameras - anyone who wants their photos to really show their items correctly should use a full-feature camera, not a phone. Sellers can also drastically change the appearance of a color with their photo program settings. So NEVER depend on a color to be just as it's shown on your screen. I can't tell you how many times I felt my heart flutter at the sight of a beautiful purple
Coach in an Ebay listing, only to find out after reading the description that it was actually brown.
Coach did a yearly Resort collection for a while in the 90s, and also did a few special and exclusive colors for some of their large department store partners, in fact they still do. So there's always a tiny chance that a unique color might have been used in a genuine bag.