I'm trying to make some dark colors *black/grey/dark blue* into a yellow or golden color.

Does anyone have any suggestions.

I'm using Photoshop CS2

How much detail do you need to preserve? I think it'd be easiest to desaturate the area, lighten up the grey that leaves behind and then apply the yellow over top.

Yeah, desaturate the area and then play with the lightness and brightness both (they're different) first, but leave yourself enough gray to give the yellow something to "stick to" and not lose all the detail. You'll probably need to saturate the yellow a lot too, so it'll look bright and true yellow and not a sickly brownish color. Also, experiment with contrast to go for a realistic look, but depending on what you're doing you may not be able to get a good result.

Assuming you're talking about digibashing, that is.

Has anyone tried either manually painting? or perhaps ramping up the contrast to max a few times and then painting out the static that it creates? It's been a while since I touched Photoshop for this... and I'm in Linux.
Light to dark and vice versa definitely produce these contrast problems. I really hate it. Nothing like wanting to do a digital repaint and then realizing the original has colors that are too light or dark to easily do.

Using the paintbrush tool is definitely something that shouldn't be unheard of if you're wanting to do a good digibash. This is especially true if the toy you're starting with a toy that has weird or unusual paint applications, like battle damage or "dirt" for example.

Absolutely. There is no way that calculations can translate a flat color selection into a metallic color. One could use filters like emboss and chrome, and do several color overlays, but ultimately that becomes comparable in time and effort as using the paintbrush tool if one desires lights sources that make sense.

I really wish I could see what the source image is that this person is working on, the poster ignored my requests for screencaps in another thread in General Discussion; I'm curious to see what exactly it is that they're doing that the 'Select' > 'Color range' > 'Variations' (or hue/saturation and brightness/contrast) advice that I already gave them can't dispatch.