  We study the light scattering properties of moderately large dust aggregates
($0.8\mu m \lesssim R \lesssim 2.0\mu m$) with a wide variation of porosity
($\mathcal{P}$) from 0.57 to 0.98. The computations are performed using the
Superposition T-matrix code with BAM2 cluster ($\mathcal{P} \sim 0.57-0.64$),
BAM1 cluster ($\mathcal{P} \sim 0.74$), BA or BPCA cluster ($\mathcal{P} \sim
0.85-0.87$) and BCCA cluster ($\mathcal{P} \sim 0.98$). The effect of aggregate
size parameter ($X$) on the light scattering properties of aggregates (BA and
BAM2) having different porosities is explored in this study. We find that the
positive polarization maximum ($P_{max}$), the amplitude of the negative
polarization ($P_{min}$) and phase function at the exact backscattering
direction ($S_{11}$(180$^\circ$)) are correlated with the porosity of
aggregates. Compact aggregates show deeper negative polarization as compared to
porous aggregates when the characteristic radius ($R$) of the aggregates are
considered to be the same. Further lower porosity aggregates show higher
$S_{11}$(180$^\circ$) and vice versa. When $\mathcal{P}$ is increased in a
range from 0.64 to 0.98, both ${S}_{11}(180^\circ$) and $P_{min}$ decrease
linearly, whereas P$_{max}$ increases linearly. We also find that the porosity
of the aggregates plays a crucial role in determining the polarimetric color
for high absorbing organic refractories. The compact clusters (BAM1 and BAM2)
show the negative polarimetric color whereas BA clusters show almost positive
polarimetric color at all values of scattering angle. We have also made some
comparisons of our simulated results with PROGRA$^2$ experimental results.
