  Transport coefficients serve as important probes in characterizing the QCD
matter created in high-energy heavy-ion collisions. Thermal and electrical
conductivities as transport coefficients have got special significance in
studying the time evolution of the created matter. We have adopted color string
percolation approach for the estimation of thermal conductivity ($\kappa$),
electrical conductivity ($\sigma_{el}$) and their ratio, which is popularly
known as Wiedemann-Franz law in condensed matter physics. The ratio
$\kappa/\sigma_{el}T$, which is also known as Lorenz number ($\mathbb{L}$) is
studied as a function of temperature and is compared with various theoretical
calculations. We observe that the thermal conductivity for hot QCD medium is
almost temperature independent in the present formalism and matches with the
results obtained in ideal equation of state (EOS) for quark-gluon plasma with
fixed coupling constant ($\alpha_s$). The obtained Lorenz number is compared
with the Stefan-Boltzmann limit for an ideal gas. We observe that a hot QCD
medium with color degrees of freedom behaves like a free electron gas.
