Update custom.css

Author: razorblade23

src/css/custom.css

@@ -19,7 +19,7 @@
 
 /* For readability concerns, you should choose a lighter palette in dark mode. */
 [data-theme='dark'] {
-  --ifm-color-primary: #10054f;
+  --ifm-color-primary: #180775;
   --ifm-color-primary-dark: #21af90;
   --ifm-color-primary-darker: #1fa588;
   --ifm-color-primary-darkest: #1a8870;