Here are a few options:
data t;
infile cards;
input t $8.;
length solution1 solution2 solution3 $5.;
solution1=scan(t,1,':')||':'||scan(t,2,':');
solution2=put(input(t,time8.),time5.);
solution3=reverse(substr(reverse(trim(left(t))),4));
cards;
8:00:00
7:45:00
10:00:00
;