@beikeland I am not a frontend developer so, I only know the “sledgehammer method”. Try to add something similar to the following to the afterRender function, see index-items.coffee#L179. It works for me but has the glitch: initially, the slider has the default background color.
$(elements).find('input').change ->
v = $(this).val()
x = 0
if v > 0
if v < 100
x = 128
else
x= 192
val = val = Math.round(v * 64 / 100) + x
rgb = [val, val, val].join()
$(this).next().css("background-color", "rgb(" + rgb + ")")
$(this).next().children("div").css("background-color", "rgb(" + rgb + ")")
"It always takes longer than you expect, even when you take into account Hofstadter's Law.", Hofstadter's Law