Hello everyone ;)
The bottom of these stones are dark. The red and yellow colors are not cover well, so these colors are not visible on the dark surface. That's why first I used white to paint the lines on the stone. Then I used red and yellow on these white lines. Next the red and yellow color look more saturated and visible.
How I painted this stone you can find in the video about base, in this minute 40:06
I hope you like it
Have a nice painting;)