girls generally have white or beige, and boys generally have black, but if ure buying second hand and black is whats available, then you could either get some white boot covers, or wear over the boot tights(the post about the not wearing boot covers in competitions, generally in a competition your choices are nice clean white skates, or over the boot tights, so you could get black if you wanted)
But on that note, if your buying second hand try asking around the skaters that look like theyve been going for a while, chances are theyll have several old pairs of skates that you could try.