Pretty much:
Blue Tickets are obtained from the event stages and are used to vote in the Popularity Poll.
White Tickets are obtained from all stages and are used to vote in a specific category. Three Categories are:
[1] The Knight that you want a new 6* version of.
[2] The Knight that you want a new 5* version of.
[3] The Knight that you want a new 5* version of out of all Flower Knights released since February 2018.