There are many many charts about kelvins as they pertain to chlorophyll activity. Here are just a select few I have chosen to show here. In these charts you will see what color spectrum (color temp / kelvin) as well as it's studied effects on chlorophyll (what helps plants grow) In flower you need a red spectrum because of the type of hormones it activated in growing. If you were to use a blue spec for flower you would get more leaf > bud ratio due to the hormonal imbalance caused by the lighting.
Here are some pictures of the charts.
http://futuregarden.com/lighting/PAR_chart.jpg
http://i138.photobucket.com/albums/q261/newt_album/chlorophyll.jpg
http://www.life.illinois.edu/govindjee/paper/fig5.gif
http://3.bp.blogspot.com/_cwbt2D65i9k/R2LFrYW5n7I/AAAAAAAABdc/Wv2F1RzAF0k/s320/Chlorophyll.jpg
The last few are a little more difficult to understand if you don't understand a slightly more advanced botanical study chart. Hope this helps. I will look up something else for your "argument" to be settled with
The 6500k are the blue and are used for veg cycles. The 2300k is the spectrum you want for flower.
There are also things on some bulbs that say "soft / cool" and some that say "warm" watt bulbs. You can find nearly any bulb in any color. Here is a link for a site for bulbs / lamps.
www.1000bulbs.com