Theme color key for multi line selection

[Proful]

I want to use one color for the 3 line selected. Below selections looks more cluttered.
Can I customise via a theme key?

[the-mikedavis]

The ui.selection key is used to theme selections (note that the cursor is themed by ui.cursor though). Also see https://docs.helix-editor.com/master/themes.html

[Proful]

Thanks.

Is it possible to change style of selection of entire line vs single word (two different style).

I'm happy with default selection of a word. I don't want to change that style.
"ui.selection" = { modifiers = [ "reversed"] }

However, when selecting an entire line or multiple line, I want one single background.

[the-mikedavis]

Is it possible to change style of selection of entire line vs single word

No this is not currently possible