To send a color to your group, simply touch the top of your lamp for 1 second. When a lamp is touched, all the lamps in the group will flash for about 30 seconds before staying on for 30 minutes by default. The flashing indicates that someone has just touched their lamp to send a color.
To send a color through the Luvlink App, just tap on the hand icon on your lamp and your color will be instantly sent to your group - without needing to physically touch your lamp!