Give priority to clarity before style.
Edit to answer the question more directly: In a stacked bar where all values are evenly important make them distinguishable from each other. I wouldn't call the colors in your second example eye-soothing as they need more effort to distinguish. It also has many values, is this graph efficient enough (does it tell a story)? The first graph has not too many colors and is pretty safe to use concerning color-blindness. Read on, my previous answer was more general.
Should colors match with the style guide colors?
Is it only a eye-catcher that is more promotional than informative?
Giving priority to the style guide and beautification probably justifies a less informative graph.
In your case it looks more like informative graphs.
Give priority to a style that makes the graph more informative and easier to read. This means the choice of color has to help read the story more efficiently.
With story I mean the purpose of the graph, the story you try to tell behind it.
If it's a graph with a bar for each product and you want to point out how your new product is selling,
it is possible to make all products the same color and the new product a different one so it will stand out. If you use red and green for example this extra reading aid will be less effective for someone with color-blindness. But if red and green represent good and bad results and is very important to communicate, this might be a sacrifice to make.
See my example, these are not exactly eye-soothing colors but serve their purpose. For people with color-blindness you can add texture, a label or remove the red color from the bars leaving only the green one filled. The latter being my favourite choice in this example case, I like to reduce the style to a minimum.
There are complete books about this and I suggest to read at least one.