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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 

Explanation:

• awk -F: start awk treating colon as a fields delimiter
• NR==FNR{} process only the first file
• a[$1]=$2;next build an array a indexed by the first field with values of the second field then skip to the next row
• a[$2]{} process only if value of previously build array with the index of the current second field is not empty (this is done only for the file2, because of the next word in the previous expression)
• print $1":"$2":"a[$2] print everything as desired

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 

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 

Explanation:

• awk -F: start awk treating colon as a fields delimiter
• NR==FNR{} process only the first file
• a[$1]=$2;next build an array a indexed by the first field with values of the second field then skip to the next row
• a[$2]{} process only if value of previously build array with the index of the current second field is not empty (this is done only for the file2, because of the next word in the previous expression)
• print $1":"$2":"a[$2] print everything as desired

After question edit:

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

Output:

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

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 

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 

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 

Explanation:

• awk -F: start awk treating colon as a fields delimiter
• NR==FNR{} process only the first file
• a[$1]=$2;next build an array a indexed by the first field with values of the second field then skip to the next row
• a[$2]{} process only if value of previously build array with the index of the current second field is not empty (this is done only for the file2, because of the next word in the previous expression)
• print $1":"$2":"a[$2] print everything as desired

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 

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 

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 

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