Delete old Studio skin.

common/static/js/vendor/tiny_mce/skins/studio/content.inline.min.css

-.mce-object{border:1px dotted #3a3a3a;background:#d5d5d5 url(img/object.gif) no-repeat center}.mce-pagebreak{cursor:default;display:block;border:0;width:100%;height:5px;border:1px dashed #666;margin-top:15px}.mce-item-anchor{cursor:default;display:inline-block;-webkit-user-select:all;-webkit-user-modify:read-only;-moz-user-select:all;-moz-user-modify:read-only;user-select:all;user-modify:read-only;width:9px!important;height:9px!important;border:1px dotted #3a3a3a;background:#d5d5d5 url(img/anchor.gif) no-repeat center}.mce-nbsp{background:#AAA}hr{cursor:default}.mce-match-marker{background:#AAA;color:#fff}.mce-match-marker-selected{background:#39f;color:#fff}.mce-spellchecker-word{background:url(img/wline.gif) repeat-x bottom left;cursor:default}.mce-item-table,.mce-item-table td,.mce-item-table th,.mce-item-table caption{border:1px dashed #BBB}td.mce-item-selected,th.mce-item-selected{background-color:#39f!important}.mce-edit-focus{outline:1px dotted #333}
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common/static/js/vendor/tiny_mce/skins/studio/content.min.css

-body{background-color:#fff;font-family:Verdana,Arial,Helvetica,sans-serif;font-size:11px;scrollbar-3dlight-color:#f0f0ee;scrollbar-arrow-color:#676662;scrollbar-base-color:#f0f0ee;scrollbar-darkshadow-color:#ddd;scrollbar-face-color:#e0e0dd;scrollbar-highlight-color:#f0f0ee;scrollbar-shadow-color:#f0f0ee;scrollbar-track-color:#f5f5f5}td,th{font-family:Verdana,Arial,Helvetica,sans-serif;font-size:11px}.mce-object{border:1px dotted #3a3a3a;background:#d5d5d5 url(img/object.gif) no-repeat center}.mce-pagebreak{cursor:default;display:block;border:0;width:100%;height:5px;border:1px dashed #666;margin-top:15px}.mce-item-anchor{cursor:default;display:inline-block;-webkit-user-select:all;-webkit-user-modify:read-only;-moz-user-select:all;-moz-user-modify:read-only;user-select:all;user-modify:read-only;width:9px!important;height:9px!important;border:1px dotted #3a3a3a;background:#d5d5d5 url(img/anchor.gif) no-repeat center}.mce-nbsp{background:#AAA}hr{cursor:default}.mce-match-marker{background:#AAA;color:#fff}.mce-match-marker-selected{background:#39f;color:#fff}.mce-spellchecker-word{background:url(img/wline.gif) repeat-x bottom left;cursor:default}.mce-item-table,.mce-item-table td,.mce-item-table th,.mce-item-table caption{border:1px dashed #BBB}td.mce-item-selected,th.mce-item-selected{background-color:#39f!important}.mce-edit-focus{outline:1px dotted #333}
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common/static/js/vendor/tiny_mce/skins/studio/fonts/readme.md

-Icons are generated and provided by the http://icomoon.io service.

common/static/js/vendor/tiny_mce/skins/studio/skin.json

-{
-	"skin-name": "studio",
-	"preview-bg": "#eeeeee",
-	"text": "#333333",
-	"text-inverse": "#ffffff",
-	"text-disabled": "#aaaaaa",
-	"has-gradients": false,
-	"has-radius": false,
-	"has-boxshadow": false,
-	"btn-text": "#000000",
-	"btn-text-shadow": "#ccd7e3",
-	"btn-bg": "#ccd7e3",
-	"btn-bg-hlight": "#ccd7e3",
-	"btn-border-top": "#ccd7e3",
-	"btn-border-right": "#ccd7e3",
-	"btn-border-bottom": "#ccd7e3",
-	"btn-border-left": "#ccd7e3",
-	"btn-split-border": "rgba(0, 0, 0, 0)",
-	"btn-primary-text": "#ffffff",
-	"btn-primary-text-shadow": "#333333",
-	"btn-primary-bg": "#0088cc",
-	"btn-primary-bg-hlight": "#0044cc",
-	"menu-bg": "#ffffff",
-	"menu-border": "rgba(0,0,0,0.2)",
-	"menuitem-text": "#333333",
-	"menuitem-bg-selected": "#0088cc",
-	"menuitem-bg-selected-hlight": "#0077b3",
-	"menuitem-separator-top": "#cbcbcb",
-	"menuitem-separator-bottom": "#ffffff",
-	"menuitem-text-inverse": "#ffffff",
-	"menuitem-bg-active": "#c8def4",
-	"menuitem-text-active": "#333333",
-	"menuitem-preview-border-active": "#aaaaaa",
-	"checkbox-border": "#c5c5c5",
-	"checkbox-border-focus": "#59a5e1",
-	"panel-border": "#ccd7e3",
-	"panel-bg": "#ccd7e3",
-	"panel-bg-hlight": "#ccd7e3",
-	"textbox-bg": "#ffffff",
-	"textbox-border": "#c5c5c5",
-	"textbox-border-focus": "#59a5e1",
-	"window-bg": "#ffffff",
-	"window-border": "#c4c4c4",
-	"tab-bg": "#e3e3e3",
-	"tab-bg-hover": "#fdfdfd",
-	"tab-bg-active": "#fdfdfd",
-	"tab-border": "#c5c5c5",
-	"colorbtn-backcolor-bg": "#bbbbbb",
-	"grid-border": "#d6d6d6",
-	"grid-border-active": "#a1a1a1"
-}
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