I figured it out. I hope this is helpful for others too, since I’ve seen a lot of people posting similar questions about absent colour information after export.
When you are exporting, right after you choose the OBJ export file format, you are given a small selection of options/settings:
-Include hidden items too
-Include mesh bodies
-Save each first level item into seperate files
Immediately below these options, in a teeny tiny font there is a button for “Advanced Options”.
TOUCH THAT BUTTON!
and it magicaly give you the option to INCLUDE VERTEX COLORS Turn that option on.
Congratulations, the colour info should now be retained in your model.
I don’t understand why the option to include the colour info would be hidden like this, or why it would even be considered an advanced option…
…but there you go, problem hopefully solved.