When you say underlights, i assume its like when F1 races are held underlights. If i recall, its very well lit.
1080p @ 25fps is the lowest shutter speed. Slower shutter speed will capture more light.
Try it on your FPV/Phone screen. If you change 720@60fps its darker, change and 1080p@25fps and it becomes brighter.
Also lock in 100/200 ISO (higher number will capture better but will be more grainier). Lock in CLOUD for white balance. These settings will minimise the purple/yellow random tinge in the vids. And average metering will help the change in colour.
If you cant enough light, adjust to positive exposure.
If you are uncerntain, take the tips from the guys and take it a bright light parking lot and test each setting.
Post up your results and note the setting you had.