Comparison of HR8799 bcde colors inferred from the IRDIS photometry of the system to those of M, L, T field dwarfs (dots), and of young companions and red dwarfs straddling the L/T transition (green stars). Reddening vectors for a 0.5 mag K-band extinction and reddening parameters R_V = 3.1 and 5.5 are overlaid (red and blue arrows). We show the reddening vector for forsterite dust grains with size distribution centered on radii r = 0.8 μm (green arrow), r = 0.4 μm (violet-purple arrow), and r = 0.2 μm (orange arrow), as well as the vectors for different grain species in gray (A_K = 0.15 mag considered).