This particular problem, which is not to be confused with similar-looking problems with .im8 images in later versions, was a known issue with Motif:
1255448: cde on Solaris x86 has yellow tinting problem with TrueColor default visual An X server that allows changing the class of the default visual should be able to work around this.
Xorg and Xming document an option for that:
-cc int default color visual class
However passing -cc with PseudoColor or its constant from X.h (3) has no effect on the default visual reported by xdpyinfo.
Alternately the issue can be fixed by installing the appropriate Motif patch for the Solaris release (e.g. 2.5 → 103947, 2.5.1 → 104195).