xcompmgr -cCfF -t-5 -l-5 -r4.2 -o.55 -D6

xcompmgr

man xcompmgr

#!/usr/bin/perl -w

# This script is written by Andrei Perhinschi
# and is licensed under the GNU GPL license
# http://www.gnu.org/licenses/gpl.html

# Much thanks goes to Daniel Forchheimer (http://www.forchheimer.se/)
# for creating transset-df and the eutotrans
# script from which this script gets its inspiration

if ( !defined $ARGV[0] || !defined $ARGV[1] || !defined $ARGV[2] ) {
die "Usage: focustran <unfocused value> <focused value> <refresh value (secs)>\n";
}

# default values
$trans_val = $ARGV[0];
$opaque_val = $ARGV[1];
$sleep_val = $ARGV[2];

# grab all window IDs
@win_ids = `xwininfo -root -all`;
foreach my $win_id ( @win_ids ) {
unless ( $win_id =~ /has\ no\ name/ || $win_id !~ /0x/ || $win_id =~ /Desktop/ ) {
 $win_id =~ /\ \"/;
 $win_id = "$`";
 $win_id =~ s/\s//g;
 push @id_lines, $win_id;
 }
}

print "ID_LINES:@id_lines\n";

# make all windows transparent
foreach my $win_id ( @id_lines ) {
system ( "transset-df --id $win_id $trans_val" );
}

$old_id = 0;
# get currently focused window's ID
while ( 1 ) {
my $active_id = `xprop -root  | grep "_NET_ACTIVE_WINDOW(WINDOW): window id # "`;
$active_id =~ /\#\s/;
$active_id = "$'";
chomp $active_id;
# set active window to opaque_val and old window to trans_val
if ( $old_id ne $active_id ) {
 system ( "transset-df --id $active_id $opaque_val" );
 system ( "transset-df --id $old_id $trans_val" );
 }
$old_id = $active_id;
print "active_ID:$active_id\n";
select ( undef, undef, undef, $sleep_val );
}

perl focustran.pl <value to make transparent windows> <value to make opaque windows> <value to wait between loops> (I recommend 0.3-0.4)