Hmm ~ definitely the bike frame, but pale/soft and bright color probably associate with female gender (such as red, pink, yellow) and dull colour associate with male gender (such as dark brown, black, navy, dark green). Although actually it's probably because (long ago) male tend to dress more simple than female (and those dark colour can affect psychology imo such as wearing dark purple/black make me calm), and now if we put aside metrosexual male, % fashionable male is less than female. Also people with less detail-attention prefer those dull colour that tend to match with any colour (I suck at giving example but what I mean is like a bright red skinny pants have limited match for the tops, for me a black skinny pants more suitable with a colourful/pale top and a crowded (full drawing and/or colourful) top rather than red skinny pants as if it's 'too overdoing')
Then again, of course ~ nowadays there's lot of people who have interest on fashion whatever their gender is ~ but the setting in here is a common Japanese thing that being stand out is not the main plot :3