Inconsistent color on value labels

### Provide a general summary of the issue here

The color of value labels is being controlled with the `thresholdBarColor` control

### 🤔 Expected Behavior?

The label color should have it's own control or it should always stay black (as it does today when `labelPosition` is set to "side")

### 😯 Current Behavior

`thresholdBarColor` also effects the value label color, but only if the `labelPosition` is "top".

### 💁 Possible Solution

The label color should have it's own control or it should always stay black (as it does today when `labelPosition` is set to "side"). Always black is less flexible, but it will protect against in accessible text.

### 🔦 Context

_No response_

### 🖥️ Steps to Reproduce

Set `thresholdBarColor` to "True". Toggle `labelPosition` between "top" and "side".

### Version

yes

### What browsers are you seeing the problem on?

Chrome

### If other, please specify.

_No response_

### What operating system are you using?

MacOS Sequoia 15.7.3

### 🧢 Your Company/Team

_No response_

### 🕷 Tracking Issue

_No response_

Reproduce the issue by setting thresholdBarColor to "True" and toggling labelPosition between "top" and "side". Trace how those controls determine value-label color, then make the label color consistent or independently controlled while preserving accessible contrast; verify both label positions in Chrome.

Written by the indexing model from the issue text.