Linux command ls basically use the file /etc/DIR_COLORS or /etc/DIR_COLORS.xterm to define the colors used, in terms of different types of terminal windows.

You can change the definitions directly in these files to alter the colors to meet your expectation. However sometimes you do not have the write access to /etc/ thus you can set an environment variable named LS_COLORS to achieve this goal. A tool named dircolors could be used to translate the definitions in /etc/DIR_COLORS to the commands to set the LS_COLORS environment variable. Use dircolors --help to see the synopsis.

For example, I am using csh, thus I would use:

dircolors -c /etc/DIR_COLORS

Then the command gives:

setenv LS_COLORS 'no=00:fi=00:di=01;34:ln=01;36:pi=40;33:so=01;35:bd=40;33;01:cd=40;33;01:or=01;05;37;41:mi=01;05;37;41:ex=01;32:*.cmd=01;32:*.exe=01;32:*.com=01;32:*.btm=01;32:*.bat=01;32:*.sh=01;32:*.csh=01;32:*.tar=01;31:*.tgz=01;31:*.arj=01;31:*.taz=01;31:*.lzh=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.gz=01;31:*.bz2=01;31:*.bz=01;31:*.tz=01;31:*.rpm=01;31:*.cpio=01;31:*.jpg=01;35:*.gif=01;35:*.bmp=01;35:*.xbm=01;35:*.xpm=01;35:*.png=01;35:*.tif=01;35:'

Modify this value and write it to .cshrc to take effect after next sourcing of .cshrc.

Read /etc/DIR_COLORS for the definitions of each value.