You can add multiple materials to an object in Blender. In Edit Mode just select the faces of the outer part and assign them to a new material. In the example I've done this for the outer, middle (white line), and the inner part.
The "darker end" can be created with a ColorRamp and a MixRGB node in the node setup. Set the mode of the MixRGB node to Multiply and factor to 1.0. To move the "darker end" of the outer part to the bottom right I had to add a Mapping node and rotate the position a bit.
The shading for the inner area looks similar. Just swapped the grey values of the ColorRamp to darken the top right part of this area a bit.
If the colors appear too dark you might need more light in your scene. The logo on the screenshot is 3m tall (to get the shading right) and there is a 3000W point light, 3m radius (affects the shadow softness).
With a Solidify modifier you can add some depth/3D to your logo and it gets some nice light reflections. Add a plane as background to see the drop shadow if you want.
I removed the Alpha channel since it's always 1 and it had no use(?). If you activate the Node Wranger addon that ships with Blender you can press CTRL + SHIFT + LMB to get a preview of the selected node. This can help a lot to see what's going on.