how do you get custom colors/ombres in your text?
Update: I've redone this explanation in a way that should be easier to understand. You can find the post here.
Original Answer: The power of HTML! As far as I'm aware, it only works on desktop Tumblr. When making a post, there's a settings button in the top right corner of the post. Click on it and find the second section labled "Text Editor". Change it from "Rich text" to "HTML".
For the text to be one color, copy and paste "<span style="color:#hex code;'">Your text</span>" without the surrounding quotations, do not touch the quotations inside. The bolded italicized parts are what you need to replace. Your text is, obviously, your own text. Search up color picker, chose the color you want, copy the six numbers in the HEX section, and replace the "hex code" part.
To make the text gradient, I usually use this website, but you could also search up "HTML Gradient Text Generator" or something like that. For this post, however, I will be referencing the website. Once you have set everything up, copy the generated code in the second box labeled "HTML code for this text: (To use on your website)", BBcode is for something else. The additional text settings don't work, as the setup is different from tumblr's posts (or maybe I'm just stupid I know like the bare minimum of HTML), so add the text type/strikethrough/bold/italics/smaller text/link to after you've pasted the text into Tumblr. If the mess that is HTML does not work with your brain, switch the Text Editor back to Rich text to do all that, because it does usually end up in this horrifying mess:
