Color newbie: How do I keep a perceived color from changing when I add opacity? Is there a formula to use in RGBA space, or do one of the other color coordinate systems have this as one of their dimensions?
I have a specific logo color #00538FFF that I'm using in other graphics. For these other graphics, I have a front layer with a rectangle fill of this color, opacity set the 80%. The desired effect is that photos in lower layers become visible but clearly tinted in the main color.
The 80% opacity is clearly not a color match for the original RGBA #00538FFF, nor did I expect it would be.
My question is: how do I calculate the matching color at a certain opacity?
Thanks, Jeff
P.S. I am using Inkscape bzr trunk.
P.P.S. Apologies for not attaching an example, I have not been successful in attempts to subscribe to inkscape-users.