Stewart Robert Hinsley schreef
Googling for the phrase "black cedar" gives nearly a thousand hits;
restricting it to pages also referring to Thuja cuts it down to 18.
Black cedar seems to be current for Thuja occidentalis 'Nigra'.

I would understand "blue cedar" as Cedrus atlantica 'Glauca', tho' I
would use "Blue Atlas Cedar". Googling additionally finds Alaskan
Weeping Blue Cedar (Chamaecyparis nootkatensis 'Glauca Pendula), Blue
Cedar (Juniperus virginica 'Glauca'), Blue Cedar-of-Lebanon (Cedrus
libani 'Glauca'), Weeping Blue Cedar-of-Lebanon (Cedrus libani '(Glauca)
Pendula'), Oregon Blue Cedar (Chamaecyparis lawsoniana 'Oregon Blue')
and Blue Cedar (Cedrus 'Feeling Blue'), at which point I stopped looking
further.

--
Stewart Robert Hinsley

+ + +
Yes, this means descending into the depths of cultivardom.

Might be more interesting to look for the ratio between
Chamaecyparis nootkatensis and its competing names, although offhand I will
guess that it is no contest.
PvR