@orlandomr27
If you can find out the face name for inline evaluation output (perhaps ask in #cider for that) then the background colour could be changed using customize
or over-ridden using the theming layer in spacemacs
I used the theming layer to change the way symbols are highlighted by lsp in this example
https://practicalli.github.io/spacemacs/install-spacemacs/clojure-lsp/configure-lsp-and-cider.html#customising-symbol-highlighting
Thank you John. I’ll find out the face name for inline evaluation and try your advice.