  The baseline design of present XFEL projects only considers the production of
a single photon beam at fixed wavelength from each baseline undulator. At
variance, the scheme described in this paper considers the simultaneous
production of high intensity SASE FEL radiation at three different wavelengths.
We present a feasibility study of our scheme, and we make exemplifications with
parameters of the baseline SASE2 line of the European XFEL operating in
simultaneous mode at 0.05 nm, 0.15 nm and 0.4 nm. Our technique for generating
the two colors at 0.05 nm and 0.15 nm is based in essence on a "fresh bunch"
technique. For the generation of radiation at 0.4 nm we propose to use an
"afterburner" technique. Implementation of these techniques does not perturb
the baseline mode of operation of the SASE2 undulator. The present paper also
describes an efficient way to obtain a multi-user facility. It is shown that,
although the XFEL photon beam from a given undulator is meant for a single
user, movable multilayer X-ray mirrors can be used to serve many users
simultaneously. The proposed photon beam distribution system would allow to
switch the FEL beam quickly between many experiments in order to make an
efficient use of the source. Distribution of photons is achieved on the basis
of pulse trains and it is possible to distribute the multicolor photon beam
among many independent beam lines, thereby enabling many users to work in
parallel with different wavelengths.
