Why are the colors of some elements toned down?
If the colors you've chosen are not fully saturated, you're most likely creating a wireframe. Wireframe elements have toned down, more transparent colors by design, so they won't be fully saturated.
We suggest using elements from the flowchart range - they will be true to the color you've chosen from the palette. Here's an example of color differences between flowchart and wireframe elements:
Here's how you can switch from the wireframe mode to the flowchart mode to create shapes with full opacity: