I am currently trying out @kagihq

Just discovered: You can drop arbitrary CSS in your account settings and now I've got the coolest search around!

Edit:
You want this too? Go to Settings->Appearance->Custom CSS->Change

Then insert this code snippet and click Save Changes:
.body-content {
--color: oklch(63% 0.2 0);
background: linear-gradient(45deg in oklch longer hue, var(--color), var(--color));
}