Someone's jokes have a strange and lovely effect on the speaker, and the poem is an attempt to put that feeling into words. The title, "Bubbly," gives the mood away at once: this is light, happy, a little giddy. The speaker says the jokes make them feel "fuzzy and bubbly inside," which mixes a soft, cozy sensation with a fizzy, energetic one. It's the warmth of being around someone you like, combined with the rush of laughing.
The most interesting move is the comparison to "the color purple and silver mixed together." Feelings don't have colors, but the image works anyway. Purple suggests something rich and a bit dreamy, while silver adds a shimmer. The two together sound like glitter in a glass of soda. The closing lines, "Yeah, / that's about right," feel casual and self-satisfied, as if the speaker has tried a few ways of describing the feeling and finally landed on one that fits. The poem is short, playful, and quietly affectionate.