Magento – configurable product name changes to simple product name when attributes (color/size) are selected

What you described here is the exact functionality of the magento configurable products.
Take a look at this for more details: http://www.magentocommerce.com/knowledge-base/entry/tutorial-creating-a-configurable-product.
When you create a configurable product you will also have the option to add a price delta to the options you use.
So for example for the size: Size 10 can have a +3E.
The down side is that all the size 10 will have that extra charge.
Then you can set for color green a price difference of -2.
This means that when selecting size 10 and color green you will have the price: BASE+3-2 = BASE + 1.

As for the colors depending on the size, this is what Magento does.
If you create a configurable product and you create simple products for only a few variations of colors and sizes only those will be visible in the product view page

In this case the easiest way would be to create 2 color attributes. Let's say color_navigate and color_dropdown.

color_navigate would be used in the layered navigation

• type: Dropdown
• scope: Global
• Use To Create Configurable Product: No
• Use In Layered Navigation: Filterable (with results)
• Visible on Product View Page on Front-end: No
• Options: Blue, Red, Green (etc)

color_dropdown would be used for selecting a product to buy

• type: Dropdown
• scope: Global
• Use To Create Configurable Product: Yes
• Use In Layered Navigation: No
• Visible on Product View Page on Front-end: No
• Options: Royal blue, Baby blue, Dark red, Crimson Red, Army green (etc)

The only downside is that the admin needs to select a color option twice but on the frontend the result is exactly what you want