Here is a history of Delaware's football helmets-
DELAWARE
c.1959 - 1969
1969 - 1976
1977 - 1983
1984 - 2003
2004 -
Delaware began using the "winged" helmet design in 1951, and has used it continuously ever since, with only a few changes to the facemask color and perhaps some slight modifications to the shades of blue and gold having been made during the intervening years. The change from a darker blue to a nearly royal blue in 2004 is the most substantial change to the blue color of which I am aware.
Some players were using facemasks as early as 1954, but they were apparently not standard issue until about 1959. The dates of transition between facemask colors listed above are not precise, because at each change, some players continued to use the previously-used color for another year or two, or even longer. The years listed above are the approximate dates when each new color became predominant.
During at least some games in 1965 a small "D" logo was added to Delaware's helmets (photograph below); the color of the "D" is unknown to me.
Check out the website-very interesting-
http://www.nationalchamps.net/Helmet_Project/