• Back to Basics:  six matte and six shimmery “brow bone” shades (I put “brow bone” in quotations since some could be used as transition or brightening shades on other skin tones), six matte and six satin/pearl transition shades, and six matte and six shimmery crease shades; with the goal being to cover  to try and cover light/medium/dark and cool/warm skin tones for basic neutrals.  This would be part of the core collection that would only be changed to address customer feedback for a particular shade. (36 shades)
• Smoke & Mirrors:  three sets of six shades in white-to-black smoky eye, beige-to-bronze smoky eye, and mauve-to-taupe smoky eye.  These would be a mix of mattes and shimmers to add more basic type shades but would also be standard. (18 shades)
• Colors of Wonder:  I’d like to have a selection of shades that fill out the range by adding color, both in terms of brighter pops of color (like cobalt blue, chartreuse green) as well as more muted, nuanced hues (olive green, plum, lavender) — maybe around 36 shades or so that would remain part of the permanent line (until enough feedback showed that there were certain shades that weren’t working at all).  I’d then like to have a rotating, seasonal selection of 24-48 shades to address shifts in trends, seasonality, and so forth.  If there were certain shades that were particularly popular, then they might get added to the permanent line or get an extended availability window.

I think I’d prefer to launch several types of products at once rather than a single type (like eyeshadow), but my approach for developing color/finish ranges for other categories would be similar — trying to create a good spectrum of light to dark, cool to warm, matte to metallic — and encouraging and finding ways to layer and mix shades to get in-between variations in the short term.