We're looking to reproduce the way Apple applies a tint-color to their controls. We're developing a web-based product and thus have to reproduce the formula/application of the color ourselves.
Our analysis shows that its non-trivial and at the very least non-linear since some colors reproduce entirely different hues.
The prefect answer would include a formula and/or an explanation of how to calculate the gradients for the toolbar as well as the buttons on the toolbar given a Tint Color.
Take a look at the Photoshop UI Mockup design file provided by Teehan & Lax. They've implemented a lot of the Apple stuff using Photoshop standard layer effects, so you can resize them as vector graphics and re-tint them to suit your needs.