papa, mama, bye-bye, win-win, hush-hush are examples of English words formed by repeating syllables (well,  somewhat childish?). Perhaps because common Chinese words are mostly one or two syllables, syllable (or word) duplication plays a bigger role, and  many words (verbs, adjectives, adverbs, etc) can be repeated to form new words or serve various functions in the sentence. Taishanese shares this attribute, and an added twist: there exists in Taishanese a form of  monosyllabic adjectival word repetition combined with tone change to indicate different degrees of intensity -- a mechanism also found with less frequency in Cantonese but not in Mandarin.

Let's take color as an example. 红[hǝŋ22] is red. 红红[hǝŋ22 hǝŋ225], with a rising tone repetition, isreddish or somewhat red. However, the reversed 红红[hǝŋ225 hǝŋ22], with the first syllable stretched and tone raised, means very red (scarlet?). You can click the following link to hear them: ♫.

Other popular colors, i.e. 白(white) [bak32]/[bak32 bak325]/[bak325 bak32], 黄(yellow) [vɔŋ22], 绿(green)[lǝk32], and 蓝(blue) [lam22], etc. behave the same way.

橙[tsaŋ22] (orange) is a less common color, and I've heard 橙橙 [tsaŋ22 tsaŋ225] (orange-ish) but not the high degree intensity form [tsaŋ225 tsaŋ22].

黑(black) [hak55] is an interesting case. It is certainly one of the more common colors, but the syllable already has the  highest tone level in the Taishanese tonal system, and its tone can not be raised any higher. Thus 黑黑 (blackish) becomes something like [hak55 ha:k55 ?ǝ55]. It's  as if the speaker tried, but failed, to raise the tone level of the second syllable while air was being held behind the glottal closure (waiting to be released at the  'right' raised tone level) until the glottis finally gave up  and the air burst out as [ǝ].  黑 does not have the 'very black' form.

We observed the following from the above examples:

Here is a sample list of common words that can be used this way: 软[ŋun33] soft, 硬[ŋaŋ32] hard, 肥[fi22] fat, 瘦[sǝu33] lean, 甜[hiam22] sweet, 咸[ham22] salty, 酸[ɬɔn33] sour, 辣[lat32] spicy, 长[tsiaŋ22] long, 短[?ɔn55] short, 尖[diam33] pointed, 圆[yɔn22] round, 扁[bein55] flat, 生[tsaŋ33] raw, 熟[sǝk32] cooked,  [hɔi22] itchy, [tiak33] ache, [gǝu33] tired.