diagram color, export follows current theme

packages/web/src/modals/ChooseColorModal.svelte

@@ -0,0 +1,27 @@
+<script lang="ts">
+  import ColorSelector from '../forms/ColorSelector.svelte';
+  import ModalBase from './ModalBase.svelte';
+
+  export let color;
+  export let header;
+  export let text;
+  export let onChange;
+
+  $: value = color;
+</script>
+
+<ModalBase {...$$restProps}>
+  <svelte:fragment slot="header">{header}</svelte:fragment>
+
+  <div class="m-2">
+    {text}
+  </div>
+
+  <ColorSelector
+    {value}
+    on:change={e => {
+      value = e.detail;
+      onChange(value);
+    }}
+  />
+</ModalBase>