Diff UI applies colour inconsistently

**What steps did you take:**

The Diff UI applies colour inconsistently when toggling groups.

**What happened:**

📺 [screen recording](https://user-images.githubusercontent.com/1182927/185119569-f09d9e5a-e2ce-4b7e-bf63-cf3a30e619b4.mov)


**Environment:**

- kapp version (use `kapp --version`): `0.52.0`
- OS (e.g. from `/etc/os-release`): macOS
- Kubernetes version (use `kubectl version`):
```
Client Version: version.Info{Major:"1", Minor:"23", GitVersion:"v1.23.1", GitCommit:"86ec240af8cbd1b60bcc4c03c20da9b98005b92e", GitTreeState:"clean", BuildDate:"2021-12-16T11:33:37Z", GoVersion:"go1.17.5", Compiler:"gc", Platform:"darwin/amd64"}
Server Version: version.Info{Major:"1", Minor:"23", GitVersion:"v1.23.5", GitCommit:"c285e781331a3785a7f436042c65c5641ce8a9e9", GitTreeState:"clean", BuildDate:"2022-03-24T22:06:50Z", GoVersion:"go1.17.8", Compiler:"gc", Platform:"linux/amd64"}
```

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