The phrase "shifting shadows" means that something is changing or unstable, like when shadows move around due to changing light or objects blocking it. Full definition
As the sound plays out across the monitors, projection lamps cast multiple and shifting shadows over the surrounding walls of the installation. (vilmagold.com)
The moves are designed to sideline critics, boost the number of women in senior jobs and shift shadow cabinet members who fundamentally disagree with the leader over their portfolios. (thetimes.co.uk)
Castor Gray is a beautiful red / green / gray shifting shadow that applies very well and looks nice and sparkly on. (mollyandstacie.com)