I am still not understanding your question.Thank you!
And yes. If a bird is bl/bl for the splash gene (black) and lav/lav for the lavender gene, then would the black phenotype of the splash gene show up as lavender because of the dilution of the lavender gene? (I hope this is more straightforward).
bl+/bl+, Lav+/Lav+ = Black
bl+/bl+, lav/lav = Lavender
Bl/bl+, Lav+/lav = Blue that carries lander hidden(Lav+/lav)
Bl/bl+, lav/lav = Blue and Lavender together, it's very light shade of lavender
Bl/Bl, lav/lav = Splash and Lavender together, Splash/White with lavender specks