I am using 2023.1.16 from 2021, and they changed the color of the Error code link from Red to Light Blue , making it impossible to read under Light Theme.
I have to change it to Dark Theme in order to see this important log,
is there any way I can fix it rather than using Dark Theme?
Under Preferences is a Color section, have a look if that color is configurable.
While its certainly not the best contrast and I understand the desire to change that color, I wouldn‘t call it impossible to read and I haven‘t heard a complaint like this. Perhaps you are overstating but just in case it is truly downright impossible to read for you perhaps it‘s the monitor settings making it harder for you to read. Check the brightness and contrast levels, and color temperature settings specifically.
It’s a good feature from Unity 3 or 4, no point to change it. I looked into Preference Color Section and it looks like there wasn’t any option for this
I will change the title to [feature suggest] but I think [Bug] is closer to what it is
Would love to know if you found a solution, I just found this out while starting a new 2023.2 project, and have failed to find any option to customize / revert this. I’ve confirmed that all previous unity versions I have up to and including 2022.3 have the old blue text color that was far more readable in light theme.
Yep, this is definitely a bug. Could you report it so we have an entry and you know when it’s fixed?
Already did! 
https://issuetracker.unity3d.com/issues/references-to-the-script-in-the-console-are-hard-to-read-when-using-unity-light-theme
Between that and https://issuetracker.unity3d.com/issues/rotation-quaternions-must-be-unit-length-error-appears-when-multiplying-quaternions
Unity 2023.2 tech stream feels pretty unusable (Kinematic Character Controller demo scene errors due to the above, and reading and working on any bugfixes is harder in the default light theme due to the text color change)
thank you, we have reported it, let’s fix it in 2023.3a18
thank you bro for reporting this as a bug