I think it's a bit of a stretch of the concept of "idea" to suggest that this seasons choice of fashionable colour is an "idea".
What can "memetics" inform us of the variations in fashion sense that psychology, sociology, economics, etc. can't?
I think it's probably garbage. Not a new science or subscience or necessary mapping tool, merely an invention of a new word. One that can be plugged in just about anywhere as a sloppy metaphor or meta-metaphor for the choice-selection process that's going on. Commenting on its own importance, yet never informing of anything that's actually relevant, or new. It doesn't need to--the actual sciences and tools of the topic in question are capable of doing so already.
Why is orange in this year? Memetics can't tell us, it can only broadly state/repeat "because most people prefer orange this year for some reason". Actual reasons could be:
*Variations of global dye production made orange dye favorable to manufacturers
*Donna Karen decided to use orange in her line, and generics added orange to make their clothing appear more couture
*The previous colors of the seasons were purple, blue, red, green, yellow, orange is a nice change
*India implemented a new nationalistic policy that favors their national colors, and their manufacturers are favoring orange over green
*A popular celebrity wowed the world at the Oscars by wearing a brilliant orange dress
*The Great Pumpkin finally revealed itself to Linus in Peanuts, and people want to celebrate this
*A new Wal-Mart CEO decided that since orange is his favorite color, he'd greatly favor showing orange clothing in all Wal-Marts
*We are genetically predisposed to favoring orange over other colors, except when we don't
*Due to environmental changes the air carries the orange wavelength different this season, making it more pleasing to the human eye-brain than other colors
Can memetics tell us any of this? Nope, it just tells us that "
favoring orange in fashion is a new meme!" Same deal for a more general discussion on why some societies favor certain colors, or why humans in general favor certain colors. If you want to actually know why, you call on sociology, economics, natural resources available, popular and personal psychology, brain-structure, etc. If you want to fake that you know why, you say it's because of memetics and leave it at that.