Warm colors are usually yellows, oranges, browns, yellowish-greens and orangish-reds. A warm pink is a peachy pink (as compared to a purplish-pink). A warm green is a yellowish-green (as compared to a bluish-green).
I've filled my Beach Tilda from Magnolia Stamps 2009 Lazy Summer Days collection with warm orange and yellowish-green tones.
My Longing Tilda image from the Magnolia 2010 Fairy Tale collection is filled with warm tones of yellow:
The "warm" tones of Best Creation's Surf's Up double-sided glitter paper with light and dark orange Bazzill card stock make a nice background for another Side-Step card (see my Side-Step card in cool tones here).
I used white cardstock to punch a few flowers and leaves using punch bunch small blossom, blossom corner and small birch. I filled the punched shapes using coordinating Copic "warm" colors then coated them with Diamond Stickles. A QuicKutz Accent die cut adds some swirly flair to these flower clusters.
Here's a side view of this Side-Step card showing my use of Copic's "warm" colors . . .
skin: E000, E00, YR00, R20
hair: E31, E35, E47
Tilda bathing suit/flowers/leaves: YR21, YR23, YR24, YG21, YG23, YG25
water: BG0000, 0
Tilda dress/hair bow/flowers: Y02, Y04, Y08
flowers: R21, R24, R27