Flying in unsuitable weather conditions could affect an insurance claim. The ‘UAV Forecast’ app is a tool to help a pilot decide if conditions are suitable.
UAV Forecast showing red doesn’t automatically mean you can’t fly insured, in the same way that it showing green doesn’t completely guarantee the conditions are suitable. Use it as a tool to assist your judgement (ideally in combination with other sources of info) and expect your judgement to be held to account should an incident occur.
Remember you need to config the app to your drone’s specs, such as max wind speed and types of satellite it can see, and then remember not every flight is the same. Maybe you can fly safely at 50m when the app shows red because of gusts at 120m.
Likewise, if you’re flying close to buildings rather than a big open space, you probably don’t want to be anywhere near the maximum ‘safe’ gust speed at all. But the app would still show green.