Start at the second month of the year in the Julian calendar and go backward 4 months. Combine the antepenultimate letter of that month with the ultimate letter of the month during which Daylight Savings Time began in the US prior to 2007. Add to that the antepenultimate letter of the month named for "Venerable Caesar." End with the penultimate letter of the month of the autumnal equinox. The resulting word is:
antepenultimate = coming before the next to last
penultimate = next to last
ultimate = last
The second month of the year acccording to the Julian calendar is February. Go back four months and you're at October. The antepenultimate letter of that month is "B"
Prior to 2007 Daylight Savings Time began in April in the US. The ultimate letter in April is "L"
The month named for the venerable Caesar is August and the antepenultimate letter of that month is "U"
September is the month of the autumnal equinox and the penultimate letter of that month is "E"
This gives us the word BLUE which is obviously the fifth color in a rainbow. Whew.