this will ignore `:color` if it is already a `CGColor`?

```ruby
if props[:color]
  color = props[:color].uicolor  # this is defined on UIColor, so this is safe
  if CFGetTypeID(color) != CGColorGetTypeID()
    color = color.CGColor
  end
  sublayer.backgroundColor = props[:color].uicolor.CGColor
end
```