Compile Error: error evaluating function `darken` Object of type

Hi guys, any idea how to fix this error displaying on my frontend:
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Compiler error:
Compiler error:
error evaluating function `darken` Object of type
Less_Tree_Anonymous passed to darken function.
Expecting `color`. #. Array ( [function] =>
darken [class] => Less_Functions ) index: 912
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Got this error after updating to Yjsg 2.1.0 on my joomla 3.x site. I only edited the custom.css and the footer.php on the framework so I am lost as to how I was able to have this error.

I have very limited knowledge on LESS ( i assume this has something to do with the error ) and compilation stuffs, so I hope I can get help on this one.

Thanks!

Are you sure your are posting in product assigned forum?: Yes

What is your CMS version?: Joomla 3.x

MySQL Version: 5.x

PHP version: 5.x

Link to installation: localhost

Have you edited any files? If yes tell us which ones.: Yes

Is this personal or client website?: Personal

validate your additional css, it says that is expecting color and seems like an empty value was found

Thanks for the heads up Neo, problem solved finally. Thanks for the reply, great help.

Upon reviewing the files, I noticed I left the "Link Color" with an empty value on the template (Eximium) option, so after inserting a color code, poof! Solved!