Four devices can express that one thing outranks another, and they aren't interchangeable. Here they are, ranked by how much contrast each supplies on the shipped scale and by how much damage each does when overused.
How do space, size, weight and colour rank?
Space is the strongest of the four and the most under-used. Put 0.25 inches above a heading and 0.0833 inches below it, a ratio of 3 to 1, and the heading has visibly joined the block beneath it. Space has no upper bound on the contrast it can supply, because the comparison is between a gap and no gap. It also costs nothing in ink and never competes with a chart. It's the cheapest device you have, and the one people forget.
Size comes second. On the shipped scale it gives 1.7778 times from title to body and 1.2857 times from body to caption. That supports three or four ranks and no more, so the scale stops at four levels.
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Weight is third. Going from a regular 400 to a bold 700 in a typical variable sans gives roughly 1.6 times the stem width, and the usable range across common families runs about 1.5 to 1.8. Weight is the right device for emphasis inside a line of body text, where size can't change without breaking the line. It's the wrong device for a whole block. A bold paragraph is a paragraph with no emphasis left to give.
Colour comes last. The reason is specific to analytical slides, and it has little to do with taste. On an analytical slide colour is already carrying data meaning: the accent series in a chart, the highlighted bar, the flagged row. Spend it on typographic rank and the reader has to work out which colour is a rank signal and which is a data signal. They'll get it wrong. If a slide needs colour to establish hierarchy, the type scale has usually failed, and the repair belongs in the scale. Leave the palette alone.
How do you test a visual hierarchy?
That ordering gives you a diagnostic. Open a slide, picture it in greyscale, and ask whether the ranking survives. If it does, colour is doing decorative or data work, and both are fine. If the ranking collapses, colour was propping up a hierarchy that space, size and weight should have built. That slide will fail for any reader with a colour-vision deficiency, and for every printed handout.