Several creators recommend specific settings in order for you to be able to better see their products. Sadly, some of these recommendations will lead to many people crashing more. For example, go to the top menu, Advanced → Debug Settings (press Ctrl-Alt-D to enable Advanced, if it isn't):
Similarly, there is a notecard going round which suggests settings to prevent graphics crashes. Sadly, those settings can often result in perfectly ordinary content refusing to render. So if you have changed debug settings per such a notecard, revert them.
For both the cases above, should you not remember what settings you changed, then proceed as follows:
Note: This is not the same as rainbow colors in-world.
If you see rainbow colors after logout and you have MSI True Color on your system, do the following steps in order:
Refer to http://jira.phoenixviewer.com/browse/FIRE-12561. Also see the alternate workaround at the comment dated 13/Apr/17