to investigate the dust properties in chemically unevolved galaxies [@takeuchi05].

It is possible to investigate the metallicity dependence of dust properties by sampling BCDs with a variety of metallicity. Recently @engelbracht08 have examined the metallicity dependence of dust emission in various wavelengths by using *Spitzer* data. In FIR, they have used Multiband Imaging Photometer for *Spitzer* (MIPS) 70 $\mu$m and 160 $\mu$m bands, and have shown that there is a correlation between dust temperature derived from these two bands and metallicity. This indicates the importance of studies on dust emission in a wide metallicity range.

The *AKARI* satellite [@murakami07] provides us with a good opportunity to study FIR colour–colour relations, since Far-Infrared Surveyor (FIS) on *AKARI* has four bands in FIR (65 $\mu$m, 90 $\mu$m, 140 $\mu$m, and 160 $\mu$m) [@murakami07; @kawada07]. Indeed, seven of the eight BCDs in @hirashita08 [hereafter H08] are detected at 65 $\mu$m, 90 $\mu$m, and 140 $\mu$m. This indicates that it is possible to study the FIR colour–colour relation of BCDs by using *AKARI* data. In this paper, we add four more BCDs available in the *AKARI* archive and examine the FIR colour–colour relation of BCDs. Then, we extract information on what determines or regulates 