Diagram of [25]–[60] vs. [12]–[25] IRAS colors. The IRAS color-color diagram is divided in different regions where sources with similar characteristics are located (see van der Veen & Habing 1988, for details). Standard AGB stars are represented with blue triangles (O-rich) and red squares (C-rich), pre-planetary and young planetary nebulae are represented with purple circles and the binary post-AGB stars of this work are shown with black circles.