Spawning a magma cube with glowing set to 1b, and the invisibility effect, causes the outline to be overridden to white, and rendering artifacts to occur when viewed from below. The entire magma cube turns white, and can be seen through other glowing objects.

The command used to summon the magma cube was as follows. Place in a command block or mcfunction file to reproduce. The team 'green' must also be created, with color set to green.

 
summon minecraft:magma_cube ~ ~2 ~ {NoGravity:1b,Silent:1b,Invulnerable:1b,Glowing:1b,Team:"green",PersistenceRequired:1b,NoAI:1b,CanPickUpLoot:0b,Size:1,ActiveEffects:[{Id:14b,Amplifier:255b,Duration:1000000,ShowParticles:0b}]}
 
I have also uploaded a video where you can see two identical magma cubes, where the one on the right does not have the invisibility effect. As you can see, it renders correctly with a green outline.