Spray paint is no way to get good autumn color in the garden. The healthy rich green king palm out front would look ridiculous and be very embarrassed, not to mention unable to breath, if it were painted yellow, orange and red, like the sweetgum trees that will soon be getting so colorful in the neighborhood now that the weather is getting cool.
Just like every other feature in the garden, autumn foliar color takes proper planning. Most of the plants with the most impressive autumn color happen to be substantial trees, so are not as easy to accommodate in as many situations as flowering annuals are. There are a few smaller shrubby plants and perennials that provide autumn foliar color, but almost all are deciduous, so defoliate to leave bare branches through winter.
Boston ivy (which is not really ivy) is probably the most colorful of climbing vines. It is a bit too aggressive for small spaces though, and damages painted surfaces and just about anything that it gets a hold of. It is best on concrete walls, which is why it is so prominent on freeway soundwalls and overpasses. Grapevine and wisteria are only moderately colorful.
Currant, crape myrtle, pomegranate, smoke tree and redbud are a few of the shrubby plants that provide good color in autumn. Crape myrtle and Eastern redbud are actually more commonly small trees. Many of the Japanese maples with good autumn color are small trees that stay smaller than most shrubbery.
Sweetgum, Chinese pistache, flowering pear and maidenhair tree are the best trees for autumn color, though maidenhair tree turns only bright yellow without the oranges and reds that the others get. Where well exposed, Japanese persimmon is comparable to Chinese pistache. Fruiting pear, apple, apricot, plum, prune and almond trees are not quite as colorful.
Several of the North American and European maples are remarkably colorful, but do not hold their foliage as long as sweetgum does. Silver maple and box elder (maple) happen to be less colorful than the other maples. Various poplars and locusts, as well as tulip tree and black walnut can almost get as bright yellow as maidenhair tree does.
Tony Tomeo 
Your first sentence stands as a punchy aphorism.
Sweetgum, a staple of east Texas, occasionally gets planted in Austin.
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It was the street tree in front of my home in town, and I thoroughly enjoyed it, but it is not one that I would recommend for such an application. The aggressive roots displace pavement. The structural deficient limbs fall and damage parked cars. The maces are hazardous on pavement. They are more tolerable at work, away from pavement, and the deep green redwoods are a perfect background for their exquisite foliar color through autumn.
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Virginia Creeper, https://plants.ces.ncsu.edu/plants/parthenocissus-quinquefolia/, has terrific scarlet color in the autumn. It was exported to Europe during colonization in our area, but I don’t know whether it would enjoy your climate. Here, it is one of those natives largely considered a ‘weed.’ I usually let some grow (it pops up everywhere) for its color and wildlife value. But it is highly poisonous if eaten and mildly irritating when handled. But it certainly is pretty on late fall!
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It grows on freeway soundwalls here and at least as far south as Los Angeles. It muffles the sound of traffic, and dissuades graffiti. It does not need much chill to color remarkably well. Boston ivy does the same.
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So you do have Virginia Creeper in Southern CA? That is remarkable. Yes, it is good for muffling the sound, but also for soaking up some of that air pollution from the highway and turning it into living tissue. Must be pretty growing on the sound walls!
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Virginia Creeper might be more common in Southern California. Boston ivy might be more common here. I do not know. Neither need much chill to color well.
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We don’t have Boston Ivy, but we have lots of Virginia Creeper. I was out photographing vines in fruit this morning for an article I’m working on about vines in our area, and how they interact with trees. I found some beautiful VA Creeper just heavy with fruits growing in a wild area along the James River.
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How odd that Boston ivy is more common in Los Angeles than in Virginia. Perhaps it would be redundant to Virginia creeper.
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natural autumn colour is a wonderful part of the garden this time of year
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Yes, but we do not get as much here as you experience there.
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