What will be the ideal option for hair/back light along with Diva-400 as key light.
I added Arri 650 then noticed that different color temperature will cause WB problem , I have the Sony EX1 and Canon XHA1.
My aim is to shoot one person interview mostly will be indoor.
Solution #1: John's post above: use a Diva 200 for a back light if you are using a 400 for a key.
Solution #2: are you tubing the Diva with tungsten bulbs? If they are daylight, there will be a huge difference. The cheapest way to correct that problem would be to gel the 650 (which is probably way too hot and needs to be scrimmed way down) with 1/2 CTB. The back light will then be pleasantly warm. However, if your interviewee is silver haired, add another 1/4 to 1/2 CTB to cool the light even more.
Whether you tube with tungsten or daylight, Divas tend to have a green spike. A 1/8 or 1/4 minus-green gel (magenta) should cure that. Osram tubes seem to run to a more true color.
There was a series of posts on CML about how the EX1 seems to react to Divas differently from true tungsten lights. I found no convincing posts. In any case, test with some color-correcting gels to even things out. A little trial and error and you should be good to go.
Remember, color variations run along two axes: the blue-orange axis (CTB/CT0) and the Green-Magenta axis (Plus-Green/Minus-Green.)