We consider high-harmonic generation in hydrogen atoms exposed to a superposition of two lin- early polarized laser fields with different colors. To this end, the full three-dimensional Schrödinger equation for the hydrogen atom is solved numerically to obtain the single-atom response. Phase-matching effects are subsequently taken into account in the limit of small atomic density. Our findings clearly indicate the possibility of creating isolated attosecond pulses from many-cycle ( ΔτFWHM = 19 fs) driver pulses by an appropriate tuning of the two laser frequencies, which results in control of the ionization and the recollision dynamics of the electronic wavepacket.