The green one is definitely a female, without a doubt...
The blue one is far too young to guess, his cere is still pink and may turn any color in the next months...I wouldn't make assumptions on it as of now, as most-all young Budgies (there are exceptions) start with a pink cere...So gonna have to wait on the blue one, although if you want me to guess, based on the entire bird, looks to be a female to me as well, but again, it's too early...
TO THE OP: There are a lot of variables to that general "Cere Color" rule you mentioned, it's not just blue/purple is male and tan/brown is female...For instance, if you have a Budgie with a blue cere, but it has white rings around it's nostrils, that's a female...And the "crusty" cere is not a gender-identification things at all, adult-female Budgies, when they go into breeding-season, have their ceres usually turn a very dark brown, and they also get extremely crusty/thick and look almost scabby. Then when they come out of breeding-season their ceres turn back to the color they usually are, and the thickness/crustiness goes away...
There are a ton more variables with Budgie gender-identification and hormonal cere changes, if you Google Search it, you'll find a lot of charts, photos, and great explanations of all of these rules...HOWEVER, THE BEST WAY TO GENDER IDENTIFY A BIRD IS BY DNA TESTING, EITHER ONLINE OR THROUGH YOUR CERTIFIED AVIAN VET!!! It's important to know the sex of your birds, and your green Budgies is a good example, because not only will she eventually, most-like lay infertile eggs (wouldn't you have been surprised?), but you cannot keep a male with a female in the same cage, or you will most-likely end up with fertile eggs, and unless you know what you're doing, you should not allow your birds to breed...I think that blue Budgie of your's is a female too, I may be wrong, as I said it's too early to tell yet, but I'm pretty sure. So if that's the case then no fear of baby birds with these two, however, they will both most-likely be laying infertile eggs, which you need to read-up on and be sure that you have Cuttlebones, Mineral Blocks, etc. inside of their cage at all times, as you don't want them to become egg-bound, so they need tons of Calcium, and you must make sure they are being fed a nutritious diet every day of lots of fresh veggies in addition to their pellets and seeds...