Here is a quick fix to change the directory colour from blue, which can be really hard to read on a blackbackround that for example putty.
This line with change the colour of the directories to yellow but will leave all other colours alone. You can add this to your ~/.bashrc or ~/.profile script to make permanent or create a file with this line in and run from the command line when needed eg ". ~user-name/changecolour".
export LS_COLORS=$(echo $LS_COLORS | sed "s/di=\(..\);../di=\1;93/")
Change the 93 to some other colour if you wish:
31 Red
32 Green
33 Orange
34 Blue
35 Purple
36 Cyan
37 Grey
90 Dark grey
91 Light red
92 Light green
93 Yellow
94 Light blue
95 Light purple
96 Turquoise
97 White