depanding on how you make your lumen prints, some can be preserved as nicholas showed
and using a very mild hypo dip ...

i mixed up a huge pickle jar of super saturated salt water
and will be experimenting with that soon ...
there are people who have stabilized film with it
cliveh stabilizes his salt prints with it ( as did talbot )
so my fingers are crossed that it might work with lumen prints.

maybe a super saturated salt solution can stabilize your colorful paper ?

good luck !
john