#!/bin/bash

echo -e "test1:test2:test3" | sed 's/:/\n/g' | grep 1
sed -E "s/(.*:)?([^:]*1[^:]*).*/\2/" <<< "test1:test2:test3"
sed "s/:/\n/g" <<< "test1:test2:test3" | sed -n "/1/p"
awk -v RS=":" '/1/' <<< "test1:test2:test3"
awk 'BEGIN{RS=":"} /1/' <<< "test1:test2:test3"