  In this paper, by analyzing mock images from the IllustrisTNG100-1
simulation, we examine the properties of the diffuse light and compare them to
those of central and satellite galaxies. Our findings suggest that the majority
of the diffuse light originates from satellites. This claim is supported by the
similarity between the age and metallicity distributions of the diffuse light
and those of the satellites. Notably, the color distribution of the diffuse
light gradually evolves to resemble that of the centrals at lower redshifts,
suggesting a coevolution or passive process. The radial profiles of the diffuse
light reveal distinct trends, with the inner regions displaying a relatively
flat distribution and the outer regions showing a descending pattern. This
finding suggests that the formation of the diffuse light is influenced by both
major mergers and stellar tidal stripping. Moreover, strong correlations are
found between the stellar mass of the diffuse light and the overall stellar
mass of the satellites, as well as between the stellar mass of the diffuse
light and the number of satellites within groups or clusters. These
relationships can be described by power-law and logarithmic functions. Overall,
the diffuse light components predominantly originate from satellites with
intermediate ages and metallicities. These satellites typically fall within the
stellar mass range of $\rm 8<\log_{10}M_{star}/M_{\odot}< 10$ and the color
range of $\rm -1<[g-r]^{0.1}< 0$. As the redshift decreases, the growth of the
diffuse light is primarily influenced by the redder satellites, while the most
massive and reddest satellites have minimal roles in its growth.
