I love styling issues... (reported to issues to Polymer/Polymer, hopefully we will get there some day)

Author: David-Mulder

demo/miscellaneous/theming.html

@@ -78,7 +78,7 @@
 					padding-right: 24px;
 				};
 
-				--paper-datatable-header-checkbox-color: rgba(255, 255, 255, var(--dark-primary-opacity));
+				--paper-datatable-header-checkbox-border-color: rgba(255, 255, 255, var(--dark-primary-opacity));
 
 				--paper-datatable-cell: {
 					color: #212121;

docs/styling.md

@@ -35,8 +35,8 @@ Sometimes you need to style content inside of a cell when using `<template>`'s.
  `--paper-datatable-divider-color` | divider color between rows | `--divider-color`
  `--paper-datatable-row-selection-color` | divider color between rows | `--paper-grey-100`
  `--paper-datatable-row-hover-color` | color of hovered row | `--paper-grey-200`
- `--paper-datatable-checkbox-color` | checkbox color | `--primary-text-color`
- `--paper-datatable-header-checkbox-color` | checkbox color | `--primary-text-color`
+ `--paper-datatable-checkbox-border-color` | checkbox color | `--primary-text-color`
+ `--paper-datatable-header-checkbox-border-color` | checkbox color | `--primary-text-color`
  `--paper-datatable-icon-color` | icon color of editable icon | `rgba(0,0,0,.54)`
 
 Mixins

paper-datatable.html

@@ -203,12 +203,14 @@
 				width: 100%;
 			}
 			paper-checkbox{
-				--paper-checkbox-unchecked-color: var(--paper-datatable-checkbox-color, --primary-text-color);
+				--paper-checkbox-unchecked-color: var(--paper-datatable-checkbox-border-color, --primary-text-color);
+				--paper-checkbox-checked-color: var(--paper-datatable-checkbox-color, --accent-color);
 				@apply(--paper-datatable-checkbox);
 			}
 			th paper-checkbox{
+				--paper-checkbox-unchecked-color: var(--paper-datatable-header-checkbox-border-color, --primary-text-color);
+				--paper-checkbox-checked-color: var(--paper-datatable-header-checkbox-color, --accent-color);
 				@apply(--paper-datatable-header-checkbox);
-				--paper-checkbox-unchecked-color: var(--paper-datatable-header-checkbox-color, --primary-text-color);
 			}
 			.partialSelectionContainer{
 				width:18px;