So far I’ve seen a green trizar and a pink Tiamad. So I was wondering, are there “shiny” versions of monsters?
Yes, they are some more:
Black shadowcat
Red stormloch
Red kamiwyrm
Gold taloknight
Blue lavaronix
Plus the 2 you mentioned.
Maybe i missed some 
Purple dolphoenix
Green Tridrakhan
Yellow Oakthulu
And pink delugazar but besides that I Think that’s it. All pointless as can’t use shinies with the same bonus as the normal. Want to use black shadow over normal in my UC team but my normal is +6 from dupes. Apparently they tried to apply the bonus but it caused some problems
Shinies should be skins or hatch at the same bonus level as the legend you have already
Shinies should have opposite movesets of their normal counterparts like shiny tri should have sleep instead of poison, shiny loch and shadow have poison instead of sleep
Skins yeah that would be awesome!