The current version of Oruxmaps includes the long awaited themeswitcher for vectormaps like the openandromaps.
Unzip the files AND folders and copy these to
../oruxmaps/mapstyles/ele-res/*.png (oder *.svg)
Once the new version of Oruxmaps with the themeswitcher is installed (updated) activate one of the themes for the openandromaps by calling the themeswitcher in Oruxmaps:
(The video-clips shows quick install of the theme and themeswitcher too)