  We employ the first-principles GW+Bethe Salpeter equation approach to study
the electronic structure and optical absorption spectra of uniaxial strained
graphene with many-electron effects included. Applied strain not only induces
an anisotropic Fermi velocity but also tilts the axis of the Dirac cone. As a
result, the optical response of strained graphene is dramatically changed; the
optical absorption is anisotropic, strongly depending on the polarization
direction of the incident light and the strain orientation; the characteristic
single optical absorption peak from {\pi}-{\pi}* transitions of pristine
graphene is split into two peaks and both display enhanced excitonic effects.
Within the infrared regime, the optical absorbance of uniaxial strained
graphene is no longer a constant because of the broken symmetry and associated
anisotropic excitonic effects. Within the visible-light regime, we observe a
prominent optical absorption peak due to a significant red shift by
electron-hole interactions, enabling us to change the visible color and
transparency of stretched graphene. Finally, we also reveal enhanced excitonic
effects within the ultraviolet regime (8 to 15 eV), where a few nearly bound
excitons are identified.
