The default colours in linux are sometimes very hard to read, notably the blue on black:

We can change the default directory listing colours by editing this file:

/etc/DIR_COLORS

or

/etc/DIR_COLORS.xterm
(in Gandi CentOS 5)

My recommendation is to change the blue to yellow for directories. Change:

DIR 00;34       # directory (blue)
to
DIR 00;33       # directory (yellow)

The result looks like this:

For a full list of colours available, consult the list below:

# Attribute codes:
# 00=none 01=bold 04=underscore 05=blink 07=reverse 08=concealed
# Text color codes:
# 30=black 31=red 32=green 33=yellow 34=blue 35=magenta 36=cyan 37=white
# Background color codes:
# 40=black 41=red 42=green 43=yellow 44=blue 45=magenta 46=cyan 47=white