Text-to-image inpainting models often exhibit an unpredictable balance among image coherence and prompt adherence. This rigidity limits their adaptability across diverse scenarios, including coarse masks, non-object, and interaction prompts. Recognizing this instability as an indicator of learned generation diversity, we aim to control model behavior for given objective. We propose Empirical Feature Intervention (EFI), a metric-agnostic framework that precomputes how feature interventions influence evaluation metrics—such as CLIP, Human Preference Score (HPS), and Image Reward (IR). Building on EFI, we introduce FreeCond, a free-of-cost framework that applies two simple input interventions (Image Frequency and Mask Value Modulation), these interventions can be further optimized via Surrogate Intervention Optimization (SIO) based on a surrogate model regressed with precomputed EFI data. FreeCond enables real-time, user-interactive control of pretrained models without retraining or architectural modifications. Also, to benchmark performance on challenging settings, we present FCIBench. Experiments on EditBench, BrushBench, and FCIBench demonstrate that FreeCond substantially improves CLIP, HPS, and IR metrics by up to 22%, 8%, and 54%, respectively.

Accurate color alignment in text-to-image (T2I) generation is critical for applications such as fashion, product visualization, and interior design, yet current diffusion models struggle with nuanced and compound color terms (e.g., Tiffany blue, baby pink), often producing images that are misaligned with human intent. Existing approaches rely on cross-attention manipulation, reference images, or fine-tuning but fail to systematically resolve ambiguous color descriptions. To precisely render colors under prompt ambiguity, we propose a training-free framework that enhances color fidelity by leveraging a large language model (LLM) to disambiguate color-related prompts and guiding color blending operations directly in the text embedding space. Our method first employs a large language model (LLM) to resolve ambiguous color terms in the text prompt, and then refines the text embeddings based on the spatial relationships of the resulting color terms in the CIELab color space. Unlike prior methods, our approach improves color accuracy without requiring additional training or external reference images. Experimental results demonstrate that our framework improves color alignment without compromising image quality, bridging the gap between text semantics and visual generation. All supplementary materials are available at https://Sung-Lin.github.io/TintBench/.