define default button style

theme.json

@@ -238,6 +238,25 @@
         "color": {
           "text": "var(--wp--preset--color--main-purple)"
         }
+      },
+      "core/button": {
+        "color": {
+          "background": "#E8BFE2",
+          "text": "var(--wp--preset--color--contrast)"
+        },
+        "spacing": {
+          "padding": {
+            "top": "1em",
+            "bottom": "1em",
+            "right": "2em",
+            "left": "2em"
+          }
+        },
+        "border": {
+          "color": "#000",
+          "width": "1px",
+          "radius": "50%"
+        }
       }
     },
     "elements": {