In November 1955, the document Maxima redemptionis nostrae was promulgated, This made the new Easter Vigil obligatory. It also changed the Holy Week rites. The explanation would be too long (even for this piece) so I’ll just point out the main things:
PALM SUNDAY:
The “Asperges me” was abolished
The entire ceremony of the fore-mass was abolished. Before 1955, the blessing of the palms resembled a Mass. It has its own Epistle, Gospel, Preface and a Sanctus and was thus known as the fore Mass.
Various aspects of the procession were changed. Palms were held by the laity and blessed instead of being blessed then distributed. An alternative was blessing the palms at a table in the sanctuary- previously it was dome at the altar.
The ceremony whereby at the return to the Church, the door was closed, and ‘Gloria, laus et honour’ was chanted, before the door was opened after the subdeacon knocked three times with the foot of the cross was abolished. The colour of the vestments at the procession became red. The ceremonies for the reading of the Gospel were changed.
The Prayers at the foot of the altar including the Confiteor were omitted.
The Gospel was shortened and its ceremonies changed.
The Last Gospel was omitted.
MAUNDY THURSDAY
The washing of the feet took place within the Mass instead of after it. The bishop no longer washed the feet of 13 men but 12.
The Confiteor before communion was omitted for the first time.
The Agnus Dei was changed- ‘miserere nobis’ was said thrice.
The prayer ‘Domine Jesu Christi’ was omitted.
The Last Gospel and Blessing were omitted at the end of the Mass.
GOOD FRIDAY
The blessing before the Gospel was omitted and its veremonies changed slightly.
To the prayer for the Jews was added the words “Let us pray. Let us kneel. Arise”.
The ceremonies for the Adoration of the Cross were slightly changed.
At the end of the adoration, the hymn Vexilla Regis was usually sung as the Sacred Host consecrated the previous day was born back to the altar. This was omitted in the new service, and three antiphons prescribed instead.
The Mass of the Presanctified (a service which incorporated the ceremonies and prayers of the Mass but omitted the Offertory Prayers [though not the prayers when incensing], Secret and Canon) was abolished and replaced with Communion. The priest and people together said the Our Father.
The vestments and the colour were changed slightly. From black, violet was used for the communion. A cope was also used instead of a black chasuble and a dalmatic and tunicle instead of the folded chasubles and stolone (a broad stole).(Originally, folded chasubles and the broad stole were worn by the deacon and subdeacon- a carryover from the practice when all, even the acolytes wore chasubles. The dalmatic and the tunicle were for more festive occasions)
The altars were also stripped even more thoroughly in the new services whereas in the old, for example, candles still remained but they were changed to unbleached ones (yellow)
For a more detailed comparison I would suggest the following article critical of the reforms:
perso.orange.fr/civitas.dei/gromier.htm
Later, the ceremony of the Vigil of Pentecost, which resembled that of the Vigil of Easter, with prophecies, the blessing of water, etc. was abolished.
If you would like to see some pictures of the Holy Week rites as they were before:
jdtreat.com/sccphotos.htm
sgg.org/general-info/photo-gallery/
The first one is an Anglican Church that follows an adaptation of the Roman Missal using the rituals of 1949.
For the second, you have to click on an icon at the bottom left which looks like a table with six cells, and select the day you want. They are sedevacantists though.