Key on left should show that pods get their own color

[jsoref]

Checklist:

• I've searched in the docs and FAQ for my answer: https://bit.ly/argocd-faq.
• I've included steps to reproduce the bug.
• I've pasted the output of argocd version.

Describe the bug

#8661 introduced:

5. It is hard to distinguish the node "kind" in the view. This fix includes changing the background color for Pods. This change can be easily removed, but is included here to address this usability issue and a separate feature can be opened to perhaps customize the node colors.

Any coloration / icon distinctions should be explained in the sidebar.

To Reproduce

1. Visit https://cd.apps.argoproj.io/applications/argocd/argocd-image-updater?view=tree&resource=
2. See tile w/ colored background
3. Check the key in the sidebar to see if there's an explanation

Expected behavior

Any coloration / icon distinctions should be explained in the sidebar.

Screenshots

Version

{
    "Version": "v2.6.0+61f8876",
    "BuildDate": "2023-01-20T15:12:19Z",
    "GitCommit": "61f8876b992cc740c1902788fca2c02e9a09b758",
    "GitTreeState": "clean",
    "GoVersion": "go1.18.10",
    "Compiler": "gc",
    "Platform": "linux/amd64",
    "KustomizeVersion": "v4.5.7 2022-08-02T16:35:54Z",
    "HelmVersion": "v3.10.3+g835b733",
    "KubectlVersion": "v0.24.2",
    "JsonnetVersion": "v0.19.1"
}

Logs

Paste any relevant application logs here.