The Access Central Luminance Contrast Assessment Tool (LCAT) allows the user to enter in the LRVs, or Luminance Reflective Values, of two different products or paint colours and instantly see if the results comply.
Most paint companies will supply the LRVs for their paint range.
You can also source the LRVs from each manufacturer and they should issue a certificate detailing the LRV of each product/paint.
Please read the certificates carefully to ensure you’ve received the correct one.
You can get a copy of the LCAT here
The following image is a screenshot from Example 1 on this website.