  X-ray Free Electron Lasers (XFELs) have been proven to generate short and
powerful radiation pulses allowing for a wide class of novel experiments. If an
XFEL facility supports the generation of two X-ray pulses with different
wavelengths and controllable delay, the range of possible experiments is
broadened even further to include X-ray-pump/X-ray-probe applications. In this
work we discuss the possibility of applying a simple and cost-effective method
for producing two-color pulses at the SASE3 soft X-ray beamline of the European
XFEL. The technique is based on the installation of a magnetic chicane in the
baseline undulator and can be accomplished in several steps. We discuss the
scientific interest of this upgrade for the Small Quantum Systems (SQS)
instrument, in connection with the high-repetition rate of the European XFEL,
and we provide start-to-end simulations up to the radiation focus on the
sample, proving the feasibility of our concept.
