Green: battery OK, i.e.: no water contained in the brake fluid

Yellow: less than 1% of water content in brake fluid

Yellow/yellow: approximately 2% of water content in brake fluid

Yellow/yellow/red: approximately 3% of water content in brake fluid

The brake fluid should be changed

Yellow/yellow/red/red: at least 4% of water content in brake fluid

The brake fluid must be changed urgently, extreme danger