the QA for advanced options in dhcp it’s closed, and the package released as update for 6.6 (i don’t know why it’s not on 6.7, maybe because 6.7 is in beta)
you could try to install it manually
for dhcp on blue, it is on qa/testing…
and here: Enhancement #3238: Configure DHCP on VLANs - NethServer 6 - NethServer.org
and let us know how it works on 6.7
if you have also a 6.6, and if you have some time… feel free to test it and report on redmine 
maybe could be useful: Template for the verification process in redmine (QA)
tnx