dmesg: don't use brow/yellow in output

The color used for subsystem prefix is useless on
while background. Let's use blue.

Signed-off-by: Karel Zak <kzak@redhat.com>
libfdisk: remove fdisk_colon()

It was unnecessary overkill to have colorized "foo:" prefix in fdisk
output.

Signed-off-by: Karel Zak <kzak@redhat.com>