CAT02 and HPE triangles

Here, we investigated the CAT02 and HPE triangles in both x,y and u ′, v ′ spaces. It was found that in u ′, v ′ space, the HPE triangle is separated into two regions by the line 3u′ − 8v′ + 6 = 0, which is the u ′, v ′ image of X + Y + Z = 0 under the mapping from ( X , Y , Z ) to ( u ′, v ′). One of these two regions admits all‐positive R,G,B triplets and the other all‐negative R,G,B triplets, under the case of ( X + Y + Z ) > 0. The findings of this study explained the computation problems of CAT02 and provided methods for solving the Yellow‐Blue and Purple problems simultaneously.