Actually pbiggar is correct – the going market rate for employees (or, at least, engineers) in an acquihire is usually around $1-2MM/employee. E.g. a small startup with 4 engineers would be acquihired for $4-8MM. Thus, if this were a full acquihire and Color has 20 engineers, I'd expect the acquisition price should have been around $20-40MM, not $2-5MM.

In an acquihire like this, the acquisition price and each employee's final compensation and options grant from Apple are entirely unrelated. diego has an excellent post in this thread covering that in more detail. [1]

[1] http://news.ycombinator.com/item?id=4670637