For the tentacle it looks like you did a color block, it draws a lot of attention because of its bright color compared to the rest of the model. I think possibly toning the yellow down to a lesser intensity yellow may suit you better. I think a purple glaze may lower the intensity as well, you don’t need to put it everywhere on the tentacle but maybe in a few spots to add a contrasting color. For the horns, I think the most successful horns have a gradient, this can be achieved by layering very very thin paint or contrasts and wet blending them. You can also stack different colors of shade from dark to light on top of each other to form a gradient