The /opt command allows users to choose from a set of options. These options are specific to the current user. If you're a registered user (with a password), these options will persist; otherwise they'll be reset when your session expires. The options are not specific to your current room, they apply to anything you do with your user account.
Set a default color for your chat lines. Supported values for COLOR are: red, green, blue, gray, maroon, olive, orange, purple, teal, and new: pink (courtesy of FaeryG).
If you select sound=on, you enable notification sounds in the dice room. sound=off disables notification sounds. This option can also be toggled in the Tools tab.
Use autoexpand=on to toggle the automatic expansion of roll details which would otherwise be hidden behind the info symbol. This option can also be toggled in the Tools tab.
Turn this on to emulate the behavior of the legacy dice rooms, where you return to dice rolling mode (as opposed to chat mode) right after sending a dice roll command. When you turn this on, your chat line will be cleared with a # symbol already in place after every die roll. This option can also be toggled in the Tools tab.