This mimicking can be minimal (some partial streaking) to full blown mimicry (where the upper petals resemble almost identically the labellum itself, markings and keels).
Some breeders have been able to hybridize with a certain cymbidium hybrid, whereby some of the markings and characteristics of the labellum, have been passed onto the lower half of the sepals (what most people see as the flower's lower 2 petals). This has been termed "partially labelloid". This hybridization has been mostly along the cymbidium plant lineage of Cym. Cleo's Melody "Freakout".
Some interesting Articles about Orchid Peloria:
1) "Transcription analysis of peloric mutants of Phalaenopsis orchids derived from tissue culture", written by Ya Huei Chen, Yi Jung Tsai, Jian Zhi Huang and Fure Chyi Chen.
2) https://www.facebook.com/notes/gawler-districts-orchid-club-inc/excessive-lip-service-peloric-orchids-by-alex-challis/982907198412176/