IRAC color–color diagrams from our synthetic photometry for the 36 YSO SEDs at Stages I, II, and III (from left to right columns) with stellar masses of 0.2, 2.0, and (from top to bottom rows), and disk inclinations of 18.2° (asterisks), 49.5° (diamonds), 81.4° (filled circles), and 87.1° (pluses). The SEDs are progressively reddened up to A_KS = 8 mag using the broad-bump case of our extinction law. Color coding represents different A_KS values (red for 0 mag). All [3.6]−[4.5] and [5.8]−[8.0] colors are relative to those for A_KS = 0, and each sequence of reddening is shifted both vertically and horizontally for clear presentation. Insets show magnified CC diagrams for A_KS of up to 1 mag. Vertical lines from A_KS = 0 mag are also drawn as a guide for eyes.