$\mu$m colour, $(140/100)_\mathrm{cl}$.

We can also take two colours for our BCD sample. However, the wavelengths of the FIS bands are slightly different from the DIRBE bands. Thus, we apply the following corrections. First, we fit $A\nu^\beta B_\nu (T_\mathrm{d})$ ($A$ is a constant and $\beta$ is the emissivity index) to the 65 $\mu$m and 90 $\mu$m fluxes derive the dust temperature $T_\mathrm{d}$. We denote the dust temperature obtained in this way as $T_\mathrm{d}((65/90)_\mathrm{cl},\,\beta )$. We adopt $\beta =1$ and 2. Then, we estimate the 60 $\mu$m flux by evaluating $A\nu^\beta B_\nu (T_\mathrm{d})$ at $\lambda =60~\mu$m under the values of $A$ and $T_\mathrm{d}((65/90)_\mathrm{cl},\,\beta )$ obtained above. The same procedure is applied for the 140 $\mu$m and 90 $\mu$m fluxes to obtain the 100 $\mu$m flux. In this way, we can obtain $(60/100)_\mathrm{cl}$ and $(140/100)_\mathrm{cl}$ for the BCD sample. In Fig. \[fig:clrdat\], we show the colour–colour relation for the sample.

For comparison, we also show the data of @hibi06 for the Milky Way (the Galactic plane with Galactic latitudes of $|b|<5^\circ$) and the Magellanic Clouds in Fig. \[fig:clrdat\]. @hibi06 found that more than 90% of the data lie on a strong correlation called main correlation, which can be fitted as $$\begin{aligned}
(140/100)_\mathrm{cl}=0.65(60/100)_\mathrm{cl}^{-0.78}
