Material's RGB base color values are changed in Unlit mode when specular is greater than 0.
User repro video:
Tested in: 4.23.1 CL#9631420, 4.25 CL#11574810
Result: the values of the base color on the second material are changed when adding specular in Unlit view mode.
Expected: The base color to not be affected.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-89413 in the post.