This is the definition of color: http://dictionary.reference.com/browse/color
We may think of color as an absolute, but is it? We also learn about primary colors such as red, yellow, and blue and accept it without much question. Is a red fire truck really red though, not according to my opinionated dog. Color is more about what colors are reflected in pure light- most light isn't pure, and then it's all about how our eyes take it. How reliable are our eyes? Ask someone you know if you can borrow their glasses and wear them- that is a quick way to learn how diverse our senses are. (In some ways Autism is like trying to drive a car while wearing someone else's glasses- please don't try it.) Anyway, most of us know that dogs perceive color differently than we do. No one knows the details since no one has came and asked a dog, but it is currently accepted that they see shades of blue and yellow. Insects on the other hand can see colors such as ultra-violet which humans cannot see.
It would stand to reason that humans perceptions will also differ. While most if us know that colorblindness exists, one can reason that some cases are undiagnosed, and even those not colorblind can differ in perceptions. Anyone who has done decorating or house painting and debated with others which colors to use may know what I'm talking about. I'm not talking about differences in taste or preferences, those can be learned and affected by our culture, memories or associations... I'm talking color perception. Have you ever painted what you think is a neutral color and someone else is saying "it's pink" "it looks mauve", "no it's not it's tan", "looks more gray to me". Sometimes a light color can be seen as pure white to others. I have even read that age has an effect on our color and sound perceptions. If one goes to the paint store with a friend, two people can have fun discovering how different a color looks to us. This can lead to pointless arguments since neither side is right or wrong. It's also important to check the swatch under different lights before making a decision. On top of that the contrast with adjacent colors can affect the impact a color has on our eyes. Some more upscale paint stores list a Light Reflectance Value to give us an idea of a color's brightness, but even then a grey shade can be bright in a black room and dark in a white one. There is also RGB values to colors (red green blue) but unless your an experiences color scientist- which I'm not, this can make it even more confusing.
Another related issue is sound perception. A lot of people don't like the sound of their own voice for at least find it uncomfortable to listen to. Anytime I have recorded my voice or heard myself on a camcorder I don't recognize my own voice. Sometimes I may even sound angry when I'm not, or serious when I'm joking. It's odd how our voice may sound different to others than to our own ears.
As far as appearance in general I think anyone who has seen a side or back profile of themselves in a photograph may be surprised to see how different they look compared to the person they saw in the mirror that day. This is why department stores use three way mirrors in fitting rooms. Our mannerisms can also come off different on a camcorder then how we think we are coming off. The difference can be scary for just about anyone, but this could explain why people can come off as "geeks" while an "identical twin" with the same potential can come off as aesthetically pleasing. It goes to show how important it is to get honest advice from someone we can actually trust. Conventional wisdom says "Be yourself" or a patronizing "Why does it matter what anyone else thinks?" I mean we shouldn't care if we're comfortable with ourselves but it's only reasonable that we would be giving others the impressions that we want to give. In other words if someone knows that their clothes make them look heavier, older, too colorful, too masculine, too feminine... or their house looks cold or boring and they're fine with it than it's all good. But if someone has no idea how they're coming off to others than a true friend should be willing to give honest, respectful advice.