报错提示： 

15:23:55.172 Module build failed (from ./node_modules/@dcloudio/vue-cli-plugin-uni/packages/sass-loader/dist/cjs.js):
15:23:55.172 SassError: Undefined variable: "$u-border-color".
15:23:55.172         on line 208 of E:\xjn\project\12.29\view\node_modules\uview-ui\components\u-grid-item\u-grid-item.vue
15:23:55.172 >>       $u-grid-item-border-right-color:$u-border-color !default; 
15:23:55.187    --------------------------------------^
15:23:55.187 Module build failed (from ./node_modules/@dcloudio/vue-cli-plugin-uni/packages/sass-loader/dist/cjs.js):
15:23:55.187 SassError: Undefined variable: "$u-border-color".
15:23:55.187         on line 37 of ../../../project/12.29/view/node_modules/uview-ui/libs/css/common.scss
15:23:55.202         from line 2 of ../../../project/12.29/view/node_modules/uview-ui/index.scss
15:23:55.202         from line 68 of E:\xjn\project\12.29\view\App.vue
15:23:55.202 >>     border-color: $u-border-color!important; 
15:23:55.202    ---------------^
15:23:55.202 Module build failed (from ./node_modules/@dcloudio/vue-cli-plugin-uni/packages/sass-loader/dist/cjs.js):
15:23:55.218 SassError: Undefined variable: "$u-content-color".
15:23:55.218         on line 244 of E:\xjn\project\12.29\view\node_modules\uview-ui\components\u-loading-icon\u-loading-icon.vue
15:23:55.218 >> $u-loading-icon-text-color:$u-content-color !default;
15:23:55.218    ---------------------------^
15:23:55.233 Module build failed (from ./node_modules/@dcloudio/vue-cli-plugin-uni/packages/sass-loader/dist/cjs.js):
15:23:55.233 SassError: Undefined variable: "$u-primary".
15:23:55.233         on line 203 of E:\xjn\project\12.29\view\node_modules\uview-ui\components\u-icon\u-icon.vue
15:23:55.233 >> $u-icon-primary: $u-primary !default;
15:23:55.233    -----------------^
15:23:55.233 Module build failed (from ./node_modules/@dcloudio/vue-cli-plugin-uni/packages/sass-loader/dist/cjs.js):
15:23:55.249 SassError: Undefined variable: "$u-primary".
15:23:55.249         on line 245 of E:\xjn\project\12.29\view\node_modules\uview-ui\components\u-toast\u-toast.vue
15:23:55.249 >> $u-toast-u-type-primary-color:$u-primary !default;
15:23:55.249    ------------------------------^

解决办法：

在项目根目录的uni.scss中引入时，引用颜色scss

@import "uview-ui/theme.scss";
@import "uview-ui/index.scss";