When something in fashion is referred to being in style, or "in," this is in direct reference to multiple fashion designers showing that something. Let's say the "something" is color blocking. Upon seeing color blocking from these designers, magazines and fashion experts will say, "Color blocking is in." This is confirmed by the numerous options of color blocking garments in your local department store. "In" basically means available for sale.
When something is "out" of style, this is in direct reference to seeing something too much. This happens when designers keep producing the color blocking, and then other designers take their lead and produce their own version of color blocking. It waterfalls from high end, the most innovative, to medium end, where innovation is scaled down for the average person. Low end actually comes into play before medium end, because cheap is often faster to make than not so cheap. Think Forever 21. At this point, color blocking is available at every level: high, medium and low. This gives every consumer access to color blocking. Everyone can, will and is wearing color blocking. Now, its been seen too much, so color blocking is out. "Out" basically means too much available for sale.
IN is OUT.
When creating a fabulous wardrobe or outfit, in and out is irrelevant. There is only unique, classic and/or flattering or not unique, classic and/or flattering. Something defined as IN can be unflattering and something considered OUT can have a unique edge.
Last week, I introduced a pair of Joe's stretchy skinny jeans to a client. She loved the soft feel and perfect fit. She also loved the clean look and versatility of the dark indigo. The 5' 4" woman walked into the store wearing light wash, ill fitting, boot cut jeans. By slipping into the dark skinny jeans, she appeared 5" 8" and 10 pounds lighter. In the middle of her excitement, she turned to me and asked, "Will skinny jeans ever go out of style?"
I replied, "No, here is why...."
Skinny jeans flatter the body. Styles that flatter the body are never "out". Another example of flattering fashion always in style, the cinch at the natural waist from the 50's silhouette. It emphasizes the appearance of a small waist and womanly curves. We like that. In general we won't get tired of looking like a woman. Some designers may get tired of it, so they create other silhouettes like the drop waist of the 20's, but the high waist cinch will always be in stores whereas the drop waist will not. Although interesting, the drop waist does not flatter, so it pops in and out of stores specifically out of boredom, not beauty.
Another reason skinny jeans will never go out of style... when you tuck your jeans into boots, you want a lean, uninterrupted, "skinny" denim dissapearing into those boots. Any other jean will bulge, ripple and overflow out from the top of that boot. Not a lovely sight.
Closing tip, next time a sales associate tells you a dress, color or blouse is "in", ask her to show you something out of style. It might actually be more unique than that "in" item she handed you.