Sephiroth Spawn made a script that allows you to have slanted bars (
link).
The only thing is that you'll probably need to edit the colours if you wanted to get the exact colours, you just need to look for the lines like this:
CODE
draw_slant_bar(x, y + 18, actor.hp, actor.maxhp, bar_width, 6, bar_color = Color.new(100, 0, 0, 255), end_color = Color.new(255, 0, 0, 255))
Those last two arguments, Color.new(100, 0, 0, 255), end_color = Color.new(255, 0, 0, 255), specify the red, green and blue of the colours at the start and end of the bar respectively