g − r vs. r − z colour–colour diagram for the ring and host components of PRGs and RTGs, shown in the upper and lower panels, respectively. Blue contours denote the host components, and red contours represent the ring components of PRGs and RTGs. Additionally, the host component of DJ0240 is marked with a circle, and its ring component is indicated with a star symbol. The dashed green and solid black lines represent the best-fit line for PRGs and RTGs. The figure highlights a distinct difference in the slopes of the linear fits between PRGs and RTGs, and DJ0240 appears to align more closely with PRGs.