Assign unique ID to distinct values within Group with dplyr

Question

Problem: I need to make a unique ID field for data that has two levels of grouping. In the example code here, it is Emp and Color. The ID needs to

Answer 1

We can try

dat %>% 
   group_by(Emp) %>%
   mutate(temp = match(Color, unique(Color)),
          temp2 = duplicated(Color)+1,
          ID = sprintf("%s.%02d.%03d", Emp, temp, temp2))%>%
   select(-temp, -temp2)  
#    Emp  Color       ID
#         
#1     A    Red A.01.001
#2     A  Green A.02.001
#3     A  Green A.02.002
#4     B Orange B.01.001
#5     B Yellow B.02.001
#6     C  Brown C.01.001