We demonstrate the control of electron-electron correlation in frustrated double ionization (FDI) of the two-electron triatomic molecule D3+ when driven by two orthogonally polarized two-color laser fields. We employ a three-dimensional semiclassical model that fully accounts for the electron and nuclear motion in strong fields. We analyze the FDI probability and the distribution of the momentum of the escaping electron along the polarization direction of the longer wavelength and more intense laser field. These observables, when considered in conjunction, bear clear signatures of the prevalence or absence of electron-electron correlation in FDI, depending on the time delay between the two laser pulses. We find that D3+ is a better candidate than H2 for demonstrating also experimentally that electron-electron correlation indeed underlies FDI
