Lighter colors without ending up with pastel

I am designing something with a lot of color, but it's made as a background for a ticket, so it has to be lighter.

However, when I lighten the colors, a lot of them turn into pastel colors and that's not the desired effect of my client.

I tried explaining that any color will get a pastel-look if you make it transparent on white (or add a transparent, white layer), but just to make sure I'm correct in this, I would like to hear what you think. Is there some way to blend down a color without washing it down?