How do I change the bg color of chmod 777 directories in tcsh?

I take it that this is output from ls, rather than tab-completion of shells? (I know at least one shell which can colourise shell tab-completions but you don't say, so I'll assume ls).

Use $LS_COLORS, often initialised via the dircolors(1) command. dircolors -p to see the defaults, take the output from the two systems and diff.

Drop the desired config into ~/.dircolors and then:

set d=$HOME/.dircolors
if ( -r $d ) eval `dircolors -c $d`

[modified from the info docs for dircolors invocation, in the coreutils package]

I would suggest changing both sticky-world-write and just regular sticky (its only purpose is world-write, right? usually at least) to the same value, namely ...37;44 which is white on a blue background. Much less annoying than the typical black on yellow which always calls for your attention and there is nothing suspicious going on.

Much less annoyed now (I tended and still tend to remove the o-w from everything I can find just so it doesn't show up that way with ls ;-). At least now if it is supposed to be world writeable, I can give it sticky as well, and then it will be fine.

dircolors -c .dircolors results in a setenv LS_COLORS '...' which is for c-shell. For bourne-shell (bash), you have to use dircolors -b.