Materials are brighter in 4.24 and 4.25 than they were in 4.23. I created the same basic material in 4.23, 4.24, and 4.25 and the 4.23 iteration was slightly darker.
Found in 4.24.1 CL#10756747
Reproduced in 4.25 Main CL#10868506
1. Create a simple material in 4.23 (my setup is attached).
2. Migrate or recreate the material in 4.24 and 4.25.
3. Compare the materials brightness.
Result: The material in the newer engine versions is brighter.
Expected: The material stays the same brightness between engine versions.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-86151 in the post.