Using the color picker in Adobe XD does not copy the correct value. There are always small differences in the hex value which causes problems when trying to be very precise building for instance a style guide.
I am comparing this to the behavior in Illustrator and Photoshop and more.
Sorry that you experienced this situation. Would you be able to share an instance or the workflow, which lead to mismatched color values? I'd like to replicate it here at my end and there are a few more details that would help.
Which OS build and version of XD are you using?
Is it happening with all the files or with a specific one.
Have you experienced it while exporting the artboard?