I have a txt file that has multiple lines of the following structure:

```
@HISEQ:XXX:8:1101:11058:2481 1:N:0:ATTCCTTTTCTTTCCC
@HISEQ:XXX:8:1101:11009:2489 1:N:0:ATCACGATTATTTCCC
@HISEQ:XXX:8:1101:1414:2364 1:N:0:GCCAATATCCTTTCCC
@HISEQ:XXX:8:1101:11009:2489 1:N:0:ATCACGATTATTTCCC

```

Now I want to grep the pattern behind the last ':'

In this case it would be:

```
ATTCCTTTTCTTTCCC
ATCACGATTATTTCCC
GCCAATATCCTTTCCC
ATCACGATTATTTCCC

```

I then want to count the number of times each of those patterns was found. 

So something like this:

```
ATTCCTTTTCTTTCCC: 1
ATCACGATTATTTCCC: 2
GCCAATATCCTTTCCC: 1

```

Can this be done with bash?