The Past is a Good Indicator of the Future
Good inventory management is done mostly by using past statistical information. Your past statistics will help you predict future sales, markdowns, and stock levels. You may think looking at your reports from your POS software is enough, but good analysis also includes using your gut instincts. Your past sales history is a way to verify your current plan, but does not take into account new trends or bad purchasing from the past. If you had large sales of an item in the past, but that item was unavailable in certain colors, how would you know if those colors would have sold well?
That is where your instinct comes into play and you order according to what you think would have sold had you had data available. A sales velocity report would also have helped identify those fast selling items that you had a shortage of. Use your history and open to buy plan, but back it up with your personal instincts in the retail business.