Use red chilly powder if you need color. Add kashmiri chilly powder /paprika if you want color and less heat.
Dried red chillies I used were quite spicy. Increase or decrease the amount of red chillies to adjust according to your spice level.
When it comes to sambhar, choice of vegetables are huge. You can use potato, eggplant/brinjal, winter melon, ladysfinger/ okra, beans, cauliflower to name a few. But using too much vegetables will make the sambhar mushy.
Dont omit the drumstick, because that has a unique aroma and flavor.
You can use coriander leaves for garnish.
Adjust the liquid as needed after adding the ground spices. Add hot water as necessary.
If you like the sambhar to be thick, cook the daal with only 1 and 1/2 cups of water.
Once the sambhar cools, it tends to thicken. You can add hot water and heat it up before serving.