RAL is a system of colour definition that classifies colours by a system of numbers and letters. RAL is an independent system not affiliated with any company or brand. The RAL system has been in use since 1927. Using RAL numbers allows for nearly precise matching of colours across different brands of paint. Because RAL is a proprietary system, it is not possible to exactly translate RAL colours to other systems. However, you can get a close match by taking some careful steps.
Ensure that the lighting for your colour matching is as close to accurate as possible. If you are matching wall paint, try to perform this matching test in the actual room with both natural light and the light you have in the room.
Hold the RAL colour fan beside the paint or colour sample at the same angle as the original application. This prevents shadows or reflections from distorting the colour.
Sort through the colour fan until you have visually identified the closest possible match.
Identify the RAL number for the match.
Consult an online colour conversion chart to find the nearest match in the appropriate colour system.
Lighting is important to colour matching. Colours will appear different in natural light and the artificial light produced by different light bulbs. Always try to recreate the correct environment when matching colours. Most paint shops will have professional colour matching equipment. There are multiple RAL colour systems: RAL Classic, RAL Effect and RAL Design are the most common.