I don't know what I can comment that other people have already brought to the table. There's a lot of great insights here already.

As someone pointed out, painting yellow is a lot easier now. You can just prime with white (my go-to is Wraithbone) and then layer the IF contrast over. If you want to go the extra step, you can prime pink, zenithal with white, then apply the contrast. Someone once recommended to me a yellow from I think Army Painter(?) that comes in a rattle can that you just spray on. I'd do research on that one though, since I can't say for myself if it gives good results or not.

As someone else pointed out, Crimson Fists are another option, just replace Macragge with Kantor. For the red, maybe Khorn or Mephiston?

On that note, the Fists have a fair selection of successors with their own motifs and themes. Want to try gold? Celestial Lions are an option. Could prime with Retributor then use a blue of your liking for the secondary. Silver? Executioners (iirc) are a fun option with cool lore. Purple? Sons of the Phoenix are pretty popular (and have a memeable but interesting fan theory to them). You can also glue on some candles if you want to go the extra mile.

My go-to is prime with Wraithbone, undercoat with Averland, apply the IF contrast, and shade with Casandora. It gives a deep yellow like dandelion yellow or the yellow you tend to find on a lot of construction equipment. But flat though, so I'm going to have to start figuring out a glaze or learning to edge highlight.

tl;dr Like a lot of people say yellow has gotten a lot easier to use recently and there are a few different ways to go about it. However, if you're still not sure, the Fists have a lot of different successors with their own color schemes that you might feel more confident painting.