There is not presently a Team Color randomization feature.
However, to lessen the burden of doing this manually, remember that you can use the main Clubber List grid, then apply a filter or grouping so you have a particular group of clubbers narrowed down, say just your Sparks Grade 1 for instance. Then you can select multiple rows by holding down the Ctrl key and then clicking different (and non-contiguous) rows. Once you have all the clubbers (rows) highlighted that you want on the same team, right click one of the highlighted rows and then from the popup menu click "Set Team Color > " and select the color.