Jane over at Alle Psalite congratulates a seminarian friend on receiving the ministry of lector and in the comments box I note that the pictures from the ceremony show that the North American College still retain their 'college soutane' for service at important ceremonies.
Let me explain - currently in Rome the normal black priest's cassock (or soutane) is the seminarian's most formal outfit. Whilst it is everyday dress for some of the congretations, in general the diocesan seminaries in Rome reserve the cassock for altar service or attendance at certain lituriges and for formal occasions. Depending on the stage of formation and the custom of the particular seminary the every-day dress of the seminarian is either the Roman collar or lay-clothes. The Roman diocesan regulations specify that clerical dress is only required of seminarians after they have gone through the ceremony of 'Admisssion to Candidacy' which normally occurs a few months before dicaconate ordination. An exception to this is the practise of the North American College which insists that all its seminarians go through 'Admission to Candidacy' before they arrive in Rome to begin their theological studies. This, it seems, is a throwback to the now-defunct Italian practice of performing 'Admission to Candidacy' early in seminary formation becuase this exempted Italian seminarians from compulsory military service.
However, until the 1970s, the cassock was not the formal wear of the seminarian, but his everyday uniform and unlike today, most of the older Roman Colleges had their own distinctive style of cassock. Now, alas, it seems that only the Scottish, the students at Propaganda Fide and (on special ceremonial occasions) Americans retain the older dress. Consulting the 1900 Handbook to Christian and Ecclesiatical Rome by Tuker and Malleson and an old edition of Georgina Masson's classic Companion Guide to Rome we find the following descriptions of the seminarian dress of yore:
Seminary of the Diocese of Rome Purple Cassock and soprana with pendant strings and no sash.
Pontificio Provincale Pio Black cassock, violet sash, a full cloak
Vatican Seminary Dark purple cassock with cromson bindings and buttons, one crimson string decorated with the papal arms, buckle shoes
Capranica College Black cassock, black soprana of shiny cloth, stings, no sash, shoes with silver buckles
Propaganda Fide Black double breasted cassock, red pipings and buttons, scarlet sash and strings
Germanic College Scarlet Cassock, black sash, scarlet soprana with pendant strings (Masson notes that they had the nickname 'gamberi cotti' or 'boiled lobsters' and that their distinctive dress was imposed due to their reputation for uproarious behaviour)
Greek College Blue cassock, red sash and pipings, blue soprana with strings - out of doors: a black soprana with wide sleeves
English College Black cassock and soprana, black strings and no sash
Scots College Purple cassock with crimson sash, buttons and pipings. Black soprana with pendant strings
Irish College Black cassock with red piping, no sash, black soprana and strings
French College The first college to abandon collegiate dress for the priest's cassock, no sash
Lombard College Black cassock, violet sash, soprana and strings
Seminary of SS. Peter and Paul Priest's dress with a black sash
Belgian College Priest's dress with a black sash edged with red
North American College Double-breasted black cassock, blue pipings and buttons, crimson sash, pendant strings
South American College Black cassock with blue edgings, blue sash, black soprana and strings
Maronite College Black cassock, soprana and strings
Bohemian College Black cassock, maroon sash edged with yellow
Armenian College Black cassock with red pipings, out of doors: black coat with wide sleeves
College of St Boniface Black cassock with yellow pipings, black soprana with black pendant srings lined with red
Polish College Black cassock and soprana with green sash
Spanish College Black cassock with blue sash, round black cape with vertical blue pipings
Candadian College Priest's dress and no sash
Ruthenian College Blue cassock, soprana with strings, orange sash
Note - the Soprana was a long sleeveless coat, often with two long strings or streamers hanging from the armholes to signify the state of tuition. The 'sash' is also known as the fascia or more colloquially the 'belly band'.
Edited to Add
If you look at the photograph gallery for the cause of Servant of God Frank Parater you'll see the difference between the plain black soutane of his American seminary and his more colourful Roman outfit. It would be remiss not to link to the page of his cause and give a biretta doff to the Shrine.