Pastel colour? Which one? You didn't really say anything about what pastel colour it would be, and it most sepias and creams are pastelish. No support.
I'm kind of neutral on this. o3o I feel like this might not really work and cause problems though.
The light change in colour might not really stand out against some of the pets in their normal colours, and like with albino and the natural Uilus, they're all white so there's no way to "lighten" that colour.