With `awk`:

 awk -F: 'NR==FNR{a[$1]=$2;next}a[$2]{print $1":"$2":"a[$2]}' file1 file2

Output:

 bart:29482164591748:computer
 smithers:68468468468464:keyboard
 lisa:68468468468464:keyboard

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**After question edit:**

 awk -F: 'NR==FNR{a[$2]=$1;next}a[$1]{print a[$1]":"$1":"$2}' file1 file2

Output:

 lisa:68468468468464:keyboard
 bart:29482164591748:computer