Raster Bars a la C64

Just wondering, way back in the day there used to be a bunch of demos not to mention games that had rolling raster bar colors behind inverted text to produce a very effective looking title screens or high score tables etc, the game Alley Kat springs to mind, youtube has a good video of the C64 version so you can see what I’m talking about.
Is there a way to reproduce this effect using monogame or anything else?

On the C64, that particular effect was done by changing the foreground text colour once per raster line. On the Amiga, it was done with the Copper chip or palette animation.

As with many old-school graphic effects, it is actually more difficult to implement these days. Quite likely that effect would be done with a custom shader now.

yeah I know, I wrote games for both,
ldx #$00
lda indexcolors,x
sta $d021
via a raster interrupt per line on the background then inverted charset to see the bars, manipulate the bar table and you got rotating color bars, similar on the amiga / st .
using shaders would possibly work i’ll look into it but if anyone has done or tried something similar i’s appreciate the input, one other thing i’d also like to ask, this is gonna be hard to explain but here goes,
I need to move an alpha channel sprite over a foreground sprite, hmm, imagine a sword at 60% opacity then an alpha sprite moving across the sword to increase the opacity like a gradient giving the sword a sheen?
any ideas?

You could achieve this effect with the stencil buffer and the built in AlphaTestEffect. That way you won’t need a custom effect. Useful link: https://gamedev.stackexchange.com/a/38150

You could draw your text as the mask and scroll an image with a gradient for the colors.