Recently I read somewhere that certain orchids should be grown in clear
pots, not opaque (brick-colored) pots. Is this true? If so, which
varieties?

I have a Laeleocattleya which is 18 years old (bought as a 1 mm clone) and
only just started flowering last year, in an opaque pot. I also have a
vanilla orchid about 6 years old, should it be in a clear pot, since it's
one of those that climbs up trees, so needs more light? It hasn't flowered
yet.

s.