#!c:/foo/bar/perl.exe
use strict;
use warnings;
use feature 'say';

while (<DATA>) {
	my @f = split;
	my ($s) = $f[-1] =~ /(\S+):/;   # capture with your colon regex
	say $s;
}

__DATA__
G157    G157.2  535 3   344 344:m64019_201112_211057/51839190/ccs,m64019_201112_211057/167772263/ccs,m64019_201112_211057/152963146/ccs
G157    G157.6  535 42  276,344,365 276:m54312U_201103_152606/5964842/ccs,m54312U_201103_152606/78907467/ccs,m54312U_201103_152606/136382258/ccs,m54312U_201103_152606/124453202/ccs,m54312U_201103_152606/117441369/ccs,m54312U_201103_152606/134415958/ccs,m54312U_201103_152606/42665917/ccs,m54312U_201103_152606/20709542/ccs,m54312U_201103_152606/137956132/ccs,m54312U_201103_152606/26020309/ccs;344:m64019_201112_211057/80413080/ccs,m64019_201112_211057/20840619/ccs,m64019_201112_211057/32964769/ccs,m64019_201112_211057/119801176/ccs,m64019_201112_211057/62327216/ccs,m64019_201112_211057/155584613/ccs,m64019_201112_211057/78775365/ccs,m64019_201112_211057/85525815/ccs,m64019_201112_211057/40042591/ccs,m64019_201112_211057/129304850/ccs,m64019_201112_211057/16450019/ccs,m64019_201112_211057/127666695/ccs,m64019_201112_211057/29427856/ccs,m64019_201112_211057/171181539/ccs,m64019_201112_211057/175898871/ccs,m64019_201112_211057/28771811/ccs,m64019_201112_211057/167051372/ccs,m64019_201112_211057/25428057/ccs;365:m64019_201101_022708/103875458/ccs,m64019_201101_022708/24576259/ccs,m64019_201101_022708/67961035/ccs,m64019_201101_022708/149356854/ccs,m64019_201101_022708/5767478/ccs,m64019_201101_022708/155123744/ccs,m64019_201101_022708/125829415/ccs,m64019_201101_022708/137232674/ccs,m64019_201101_022708/83232122/ccs,m64019_201101_022708/126617353/ccs,m64019_201101_022708/64619288/ccs,m64019_201101_022708/64751219/ccs,m64019_201101_022708/132055970/ccs,m64019_201101_022708/34539631/ccs
G157    G157.9  535 4   344 344:m64019_201112_211057/80413080/ccs,m64019_201112_211057/78775365/ccs,m64019_201112_211057/85525815/ccs,m64019_201112_211057/27198805/ccs
G157    G157.11 535 6   276 276:m54312U_201103_152606/156304839/ccs,m54312U_201103_152606/15336676/ccs,m54312U_201103_152606/136382258/ccs,m54312U_201103_152606/134415958/ccs,m54312U_201103_152606/42665917/ccs,m54312U_201103_152606/20709542/ccs