It's not a console command. gui_theme is both a command line argument and a configuration option. Find the config.txt file for your operating system, then edit it in a text editor:
Locate "gui_theme" and change the 0 to 1.
You can also specify -gui_theme 1 on the command line. For example, in macOS, run this in Terminal, changing the path based on where you put the PICO-8 app:
~/PICO-8/PICO-8.app/Contents/MacOS/pico8 -gui_theme 1
Linux is similar, for wherever you put the pico8 binary. You can also do this from the Windows command prompt, though here's another way (similar to what Remagamer is describing):
[Please log in to post a comment]