To do this, we have to change the post's HTML, but I promise it's not too difficult (you can do this on your phone, but I think it's more work, so I strongly recommend you do it on your laptop/computer)
First, you'll access the JSFiddle website
If you want a gradient of just two colors, you don't need to change anything else. But if you want more colors, you will copy this code { <input id=“first” type=“color” value=“#FF0000” / > } and paste it in the line below, the only change in the code you will have to make is the number. The first line will always be "first," then "second," "third," "fourth" and so on until you reach the last line, which will always be "last."
After you do this, you will click run and the colored squares will increase
Once done, you will click on the little square and change it to the hex code. This is where Pinterest comes in, there are MANY color palettes there, just search for color palette hex and choose the colors that your heart desires.
After choosing the colors of your choice, you will press run and select this code (just press ctrl + A and then ctrl + C) and we will return to tumblr
You will click here and select for the text to be in HTML, then just paste the code you copied and the magic is done. You click on view and there will be your beautiful and colorful text.
Then you select the rich text again and can edit your post. You can add links, make it bold or italic like normal text.
Now, if you just want one color...
You will put the same hex code in those two squares on the website and select the code, and do the same procedure to bring it to tumblr
I really hope I didn't explain it in such a mediocre way