in the designer you can define the colors as HEX value with transparency.
In the blocks you can only choose between RGB values without transparency.
My problem, for example if I choose a transparent color as background in the designer and want to use it in the blocks, I have not found a solution yet
This isn’t a best solution, but you can try adding a for e.g. space on the screen through the designer, make the visibility = false, and put the background color to your liking.
Then, in the blocks do myCoolButton.background color = space1.background color