Merge colon-separated information from file1 and file2 where second field of both files matches, sorting the result based on this field - for each line, output: first 3 fields of first file, followed by first 3 fields of second file.
join -o 1.1,1.2,1.3,2.1,2.2,2.3 -j2 <(sort -k2 file1) <(sort -k2 file2)