Ok. I made this so i know how its done. You open powder toy console and change the life of the dust to something high, like 240000. Then you change the tmp to 5 and its glowing dust :).
When fireworks explode, they turn into dust which uses Life, Ctype, Flags, and Tmp variables to determine color. You can't manually change Flags variable through console yet, so glow colors in dust that are made manually are chiefly limited to shades of Cyan, Blue, and Green.