Beta 4 of X-Plane 12 Early Access is available on Steam & through the Laminar Research installer. You should be prompted to auto update the next time you launch the sim, if you haven’t already. Here is a link to Early Access release notes.
This build contains multiple crash fixes, as well as our first go at fixing the magenta (aka pink or purple) sadness. X-Plane renders magenta when it hits a numeric error (a NaN value) inside the rendering engine. There may be multiple causes of NaNs – it’s not all one bug because magenta is a symptom, not a cause, and each bug has to be squashed one by one.
Don’t be surprised if some users see less magenta in the this beta and others do not. If you still see it, please file (or re-file) a bug that includes a screenshot or two of where you see it, and any steps needed to reproduce it.